BaseTools: add CLANG35 toolchain with AARCH64 support

BaseTools: add CLANG35 toolchain with AARCH64 support

This adds support for building the AARCH64 platforms using the
Clang compiler and assembler combined with the GNU (cross-)linker.

The chosen name CLANG35 is based on version 3.5 being the oldest
supported version, but no issues are known that should prevent its
use with any later version.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Tested-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18198 6f19259b-4bc3-4df7-8a09-765794883524