[libclc] [libclc] Append file_specific_compile_options after ARG_COMPILE_FLAGS (PR #139871)

[Wenju He via cfe-commits]

wenju-he wrote:

> Sure, no problem. You can probably request [commit access](https://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access) by now, though.

thanks @frasercrmck 
I've requested at https://github.com/llvm/llvm-project/issues/140521, please help to review, thank you.

https://github.com/llvm/llvm-project/pull/139871