std: Make copy_file_range checks run at compile-time
* Avoid emitting the copy_file_range symbol at all to prevent link-time
errors.
* Fix a bug in the check logic, the has_copy_file_range_syscall was
set to the wrong value in case of ENOSYS
* If link_libc is true don't fall-back to the raw syscall approach,
there's no policy about what to do in this case but let's follow what
the other impls do.
Fixes #9146
e4225ca5f7LemonBoy committed on 6/20/2021, 5:58:10 PM· committed by Veikka Tuominenparent6de45c8