Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/include/llvm/Support/Program.h b/linux-x64/clang/include/llvm/Support/Program.h
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+//===- llvm/Support/Program.h ------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the llvm::sys::Program class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_PROGRAM_H
+#define LLVM_SUPPORT_PROGRAM_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/ErrorOr.h"
+#include <system_error>
+
+namespace llvm {
+namespace sys {
+
+  /// This is the OS-specific separator for PATH like environment variables:
+  // a colon on Unix or a semicolon on Windows.
+#if defined(LLVM_ON_UNIX)
+  const char EnvPathSeparator = ':';
+#elif defined (LLVM_ON_WIN32)
+  const char EnvPathSeparator = ';';
+#endif
+
+/// @brief This struct encapsulates information about a process.
+struct ProcessInfo {
+#if defined(LLVM_ON_UNIX)
+  typedef pid_t ProcessId;
+#elif defined(LLVM_ON_WIN32)
+  typedef unsigned long ProcessId; // Must match the type of DWORD on Windows.
+  typedef void * HANDLE; // Must match the type of HANDLE on Windows.
+  /// The handle to the process (available on Windows only).
+  HANDLE ProcessHandle;
+#else
+#error "ProcessInfo is not defined for this platform!"
+#endif
+
+  enum : ProcessId { InvalidPid = 0 };
+
+  /// The process identifier.
+  ProcessId Pid;
+
+  /// The return code, set after execution.
+  int ReturnCode;
+
+  ProcessInfo();
+};
+
+  /// \brief Find the first executable file \p Name in \p Paths.
+  ///
+  /// This does not perform hashing as a shell would but instead stats each PATH
+  /// entry individually so should generally be avoided. Core LLVM library
+  /// functions and options should instead require fully specified paths.
+  ///
+  /// \param Name name of the executable to find. If it contains any system
+  ///   slashes, it will be returned as is.
+  /// \param Paths optional list of paths to search for \p Name. If empty it
+  ///   will use the system PATH environment instead.
+  ///
+  /// \returns The fully qualified path to the first \p Name in \p Paths if it
+  ///   exists. \p Name if \p Name has slashes in it. Otherwise an error.
+  ErrorOr<std::string>
+  findProgramByName(StringRef Name, ArrayRef<StringRef> Paths = {});
+
+  // These functions change the specified standard stream (stdin or stdout) to
+  // binary mode. They return errc::success if the specified stream
+  // was changed. Otherwise a platform dependent error is returned.
+  std::error_code ChangeStdinToBinary();
+  std::error_code ChangeStdoutToBinary();
+
+  /// This function executes the program using the arguments provided.  The
+  /// invoked program will inherit the stdin, stdout, and stderr file
+  /// descriptors, the environment and other configuration settings of the
+  /// invoking program.
+  /// This function waits for the program to finish, so should be avoided in
+  /// library functions that aren't expected to block. Consider using
+  /// ExecuteNoWait() instead.
+  /// \returns an integer result code indicating the status of the program.
+  /// A zero or positive value indicates the result code of the program.
+  /// -1 indicates failure to execute
+  /// -2 indicates a crash during execution or timeout
+  int ExecuteAndWait(
+      StringRef Program, ///< Path of the program to be executed. It is
+      ///< presumed this is the result of the findProgramByName method.
+      const char **Args, ///< A vector of strings that are passed to the
+      ///< program.  The first element should be the name of the program.
+      ///< The list *must* be terminated by a null char* entry.
+      const char **Env = nullptr, ///< An optional vector of strings to use for
+      ///< the program's environment. If not provided, the current program's
+      ///< environment will be used.
+      ArrayRef<Optional<StringRef>> Redirects = {}, ///<
+      ///< An array of optional paths. Should have a size of zero or three.
+      ///< If the array is empty, no redirections are performed.
+      ///< Otherwise, the inferior process's stdin(0), stdout(1), and stderr(2)
+      ///< will be redirected to the corresponding paths, if the optional path
+      ///< is present (not \c llvm::None).
+      ///< When an empty path is passed in, the corresponding file descriptor
+      ///< will be disconnected (ie, /dev/null'd) in a portable way.
+      unsigned SecondsToWait = 0, ///< If non-zero, this specifies the amount
+      ///< of time to wait for the child process to exit. If the time
+      ///< expires, the child is killed and this call returns. If zero,
+      ///< this function will wait until the child finishes or forever if
+      ///< it doesn't.
+      unsigned MemoryLimit = 0, ///< If non-zero, this specifies max. amount
+      ///< of memory can be allocated by process. If memory usage will be
+      ///< higher limit, the child is killed and this call returns. If zero
+      ///< - no memory limit.
+      std::string *ErrMsg = nullptr, ///< If non-zero, provides a pointer to a
+      ///< string instance in which error messages will be returned. If the
+      ///< string is non-empty upon return an error occurred while invoking the
+      ///< program.
+      bool *ExecutionFailed = nullptr);
+
+  /// Similar to ExecuteAndWait, but returns immediately.
+  /// @returns The \see ProcessInfo of the newly launced process.
+  /// \note On Microsoft Windows systems, users will need to either call
+  /// \see Wait until the process finished execution or win32 CloseHandle() API
+  /// on ProcessInfo.ProcessHandle to avoid memory leaks.
+  ProcessInfo ExecuteNoWait(StringRef Program, const char **Args,
+                            const char **Env = nullptr,
+                            ArrayRef<Optional<StringRef>> Redirects = {},
+                            unsigned MemoryLimit = 0,
+                            std::string *ErrMsg = nullptr,
+                            bool *ExecutionFailed = nullptr);
+
+  /// Return true if the given arguments fit within system-specific
+  /// argument length limits.
+  bool commandLineFitsWithinSystemLimits(StringRef Program,
+                                         ArrayRef<const char *> Args);
+
+  /// File encoding options when writing contents that a non-UTF8 tool will
+  /// read (on Windows systems). For UNIX, we always use UTF-8.
+  enum WindowsEncodingMethod {
+    /// UTF-8 is the LLVM native encoding, being the same as "do not perform
+    /// encoding conversion".
+    WEM_UTF8,
+    WEM_CurrentCodePage,
+    WEM_UTF16
+  };
+
+  /// Saves the UTF8-encoded \p contents string into the file \p FileName
+  /// using a specific encoding.
+  ///
+  /// This write file function adds the possibility to choose which encoding
+  /// to use when writing a text file. On Windows, this is important when
+  /// writing files with internationalization support with an encoding that is
+  /// different from the one used in LLVM (UTF-8). We use this when writing
+  /// response files, since GCC tools on MinGW only understand legacy code
+  /// pages, and VisualStudio tools only understand UTF-16.
+  /// For UNIX, using different encodings is silently ignored, since all tools
+  /// work well with UTF-8.
+  /// This function assumes that you only use UTF-8 *text* data and will convert
+  /// it to your desired encoding before writing to the file.
+  ///
+  /// FIXME: We use EM_CurrentCodePage to write response files for GNU tools in
+  /// a MinGW/MinGW-w64 environment, which has serious flaws but currently is
+  /// our best shot to make gcc/ld understand international characters. This
+  /// should be changed as soon as binutils fix this to support UTF16 on mingw.
+  ///
+  /// \returns non-zero error_code if failed
+  std::error_code
+  writeFileWithEncoding(StringRef FileName, StringRef Contents,
+                        WindowsEncodingMethod Encoding = WEM_UTF8);
+
+  /// This function waits for the process specified by \p PI to finish.
+  /// \returns A \see ProcessInfo struct with Pid set to:
+  /// \li The process id of the child process if the child process has changed
+  /// state.
+  /// \li 0 if the child process has not changed state.
+  /// \note Users of this function should always check the ReturnCode member of
+  /// the \see ProcessInfo returned from this function.
+  ProcessInfo Wait(
+      const ProcessInfo &PI, ///< The child process that should be waited on.
+      unsigned SecondsToWait, ///< If non-zero, this specifies the amount of
+      ///< time to wait for the child process to exit. If the time expires, the
+      ///< child is killed and this function returns. If zero, this function
+      ///< will perform a non-blocking wait on the child process.
+      bool WaitUntilTerminates, ///< If true, ignores \p SecondsToWait and waits
+      ///< until child has terminated.
+      std::string *ErrMsg = nullptr ///< If non-zero, provides a pointer to a
+      ///< string instance in which error messages will be returned. If the
+      ///< string is non-empty upon return an error occurred while invoking the
+      ///< program.
+      );
+  }
+}
+
+#endif