MdePkg/ProcessorBind.h: Add ARM and AArch64 GCC macros for Clang

When compiling with Clang, we still use GNU as for the assembler, so we still need to define the GCC_ASM* macros.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg@16282 6f19259b-4bc3-4df7-8a09-765794883524