Update prebuilt Clang to r416183b from Android.

https://android.googlesource.com/platform/prebuilts/clang/host/
linux-x86/+/06a71ddac05c22edb2d10b590e1769b3f8619bef

clang 12.0.5 (based on r416183b) from build 7284624.

Change-Id: I277a316abcf47307562d8b748b84870f31a72866
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/linux-x64/clang/include/clang-tidy/misc/UnusedUsingDeclsCheck.h b/linux-x64/clang/include/clang-tidy/misc/UnusedUsingDeclsCheck.h
new file mode 100644
index 0000000..2e46f3c
--- /dev/null
+++ b/linux-x64/clang/include/clang-tidy/misc/UnusedUsingDeclsCheck.h
@@ -0,0 +1,57 @@
+//===--- UnusedUsingDeclsCheck.h - clang-tidy--------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNUSED_USING_DECLS_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNUSED_USING_DECLS_H
+
+#include "../ClangTidyCheck.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include <vector>
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+/// Finds unused using declarations.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/misc-unused-using-decls.html
+class UnusedUsingDeclsCheck : public ClangTidyCheck {
+public:
+  UnusedUsingDeclsCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  void onEndOfTranslationUnit() override;
+
+private:
+  void removeFromFoundDecls(const Decl *D);
+
+  struct UsingDeclContext {
+    explicit UsingDeclContext(const UsingDecl *FoundUsingDecl)
+        : FoundUsingDecl(FoundUsingDecl), IsUsed(false) {}
+    // A set saves all UsingShadowDecls introduced by a UsingDecl. A UsingDecl
+    // can introduce multiple UsingShadowDecls in some cases (such as
+    // overloaded functions).
+    llvm::SmallPtrSet<const Decl *, 4> UsingTargetDecls;
+    // The original UsingDecl.
+    const UsingDecl *FoundUsingDecl;
+    // The source range of the UsingDecl.
+    CharSourceRange UsingDeclRange;
+    // Whether the UsingDecl is used.
+    bool IsUsed;
+  };
+
+  std::vector<UsingDeclContext> Contexts;
+};
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_UNUSED_USING_DECLS_H