[libc] Support LIBC_COPT_USE_C_ASSERT build flag

In this mode, LIBC_ASSERT is just standard C assert.

Reviewed By: abrachet

Differential Revision: https://reviews.llvm.org/D151498

GitOrigin-RevId: 65c78933ae22a9a26b56ed763f5827765ce7eadf
1 file changed