libclc: Add -cl-no-stdinc to clang flags on clang >=13

cf3ef15a ("[OpenCL] Add builtin
declarations by default.")
 switched behaviour to include "opencl-c-base.h". We don't want or need
 that for libclc so pass the flag to revert to old behaviour.

Fixes build since cf3ef15a

Reviewed By: tstellar

Differential Revision: https://reviews.llvm.org/D99794