cmake: Add gcc support

This commit adds the option to cmake to build TF-M with GCC.

Change-Id: I7a5e3c915efa61620f1f0d34ed42cba5c174c562
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
diff --git a/cmake/Common/CompilerDetermineCXX.cmake b/cmake/Common/CompilerDetermineCXX.cmake
index d6461c1..6d1f142 100644
--- a/cmake/Common/CompilerDetermineCXX.cmake
+++ b/cmake/Common/CompilerDetermineCXX.cmake
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2017, Arm Limited. All rights reserved.
+# Copyright (c) 2017-2018, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -24,8 +24,8 @@
 	set(CMAKE_CXX_COMPILER_ID "ARMCLANG" CACHE INTERNAL "C++ compiler ID" FORCE)
 	set(ARM_TOOLCHAIN_FILE "Compiler/ARMClang-CXX")
 elseif (_CXX_COMPILER_NAME MATCHES "^.*gcc(\\.exe)?$")
-	set(CMAKE_CXX_COMPILER_ID "GNU" CACHE INTERNAL "C++ compiler ID" FORCE)
-	set(ARM_TOOLCHAIN_FILE "Compiler/GNU-CXX")
+	set(CMAKE_CXX_COMPILER_ID "GNUARM" CACHE INTERNAL "C++ compiler ID" FORCE)
+	set(ARM_TOOLCHAIN_FILE "Compiler/GNUARM-CXX")
 elseif (_CXX_COMPILER_NAME MATCHES "^.*iccarm(\\.exe)?$")
 	set(CMAKE_CXX_COMPILER_ID "IAR" CACHE INTERNAL "C++ compiler ID" FORCE)
 	set(ARM_TOOLCHAIN_FILE "Compiler/IAR-CXX")