Revert "ANDROID: enable LLVM_IAS=1 for clang's integrated assembler for x86_64"

This reverts commit b009f0a1.

Bug: 178427746
Reason for revert: syscalls.nanosleep01_32bit#syscalls.nanosleep01_32bit failing

Change-Id: I0089e40fd8e3a6aa14649ba7838851f1e247fdf0
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>