ANDROID: enable LLVM_IAS=1 for clang's integrated assembler for arm

Step 8 of:
https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/+/master/BINUTILS_KERNEL_DEPRECATION.md

Bug: 141693040
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Change-Id: I092cc14194fae5fba42c9a09b8eb8dd2adcb1377
diff --git a/build.config.arm b/build.config.arm
index 77f8dc8..d944676 100644
--- a/build.config.arm
+++ b/build.config.arm
@@ -1,5 +1,6 @@
 ARCH=arm
 
+LLVM_IAS=1
 CROSS_COMPILE=arm-linux-gnueabi-
 LINUX_GCC_CROSS_COMPILE_PREBUILTS_BIN=prebuilts/gas/linux-x86