Fix test compile errors after LLVM rebase

After the new rebase of Clang, we now support the alloc_size attribute,
so we can remove the warning about switching to alloc_size once Clang
has support.

Also fix an issue where 'false' is returned in a main method.

Test: make cts
Bug: 37752547
Change-Id: I32ee814aaa0338567cb8174a68d7ee1bfece2f75