The default host CPU for an i386 triple is typically at least an i586,
which has cmpxchg8b (Clang feature, "cx8"). Therefore,
__CLANG_ATOMIC_LLONG_LOCK_FREE is 2 on the host, but the value should
be 1 for the device.
Also, grep for __CLANG_ATOMIC_* instead of __GCC_ATOMIC_*. The CLANG
macros are always emitted, but the GCC macros are omitted for the
*-windows-msvc targets. The __GCC_HAVE_SYNC_COMPARE_AND_SWAP macro
always has GCC in its name, not CLANG, however.