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

This reverts commit c0bbbe403d6b743a17e2b99cc7375695edbd2f61.

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
diff --git a/build.config.aarch64 b/build.config.aarch64
index 97758e6..0b9adb9 100644
--- a/build.config.aarch64
+++ b/build.config.aarch64
@@ -1,5 +1,6 @@
 ARCH=arm64
 
+LLVM_IAS=1
 CROSS_COMPILE=aarch64-linux-gnu-
 LINUX_GCC_CROSS_COMPILE_PREBUILTS_BIN=prebuilts/gas/linux-x86