build native tests for 32-bit and 64-bit

32-bit tests will build into /data/nativetest
64-bit tests will build into /data/nativetest64

Change-Id: I31492c7d1273ba18bb2577fae150008a214c3bf4
Support .asm being compiled by yasm targeted for x86.

Change-Id: Icd6626a082facf920b0e49e2fbe8861e94400552
Merge "Support .asm being compiled by yasm targeted for x86."
Merge "build native tests for 32-bit and 64-bit"
Switch to 32-bit-by-default host multilib build.

Also we don't need to force LLVM built from source, for we already force
LLVM to be built as 32-bit.

Bug: 13751317
Change-Id: Ifadf1988d28b60cb06316de50f5bdc1834f1acc0
Merge "Switch to 32-bit-by-default host multilib build."
Merge branch 'master' of https://android.googlesource.com/platform/build into kk-aosp-master