Revert "Revert "Revert "Revert "ANDROID: enable LLVM_IAS=1 for clang's...

Revert "Revert "Revert "Revert "ANDROID: enable LLVM_IAS=1 for clang's integrated assembler for aarch64""""

This reverts commit c0bbbe40.

This enables clang's integrated assembler.  Previous issues were
tracked down with ARMv8.3 PAC (CONFIG_ARM64_PTR_AUTH) which has been
disabled for now.

Bug: 141693040
Bug: 173653853
Bug: 174803347
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Change-Id: I85d132d0cf3470d9afaa7f1b65ac73efc74cfea9