[libc] Partially implement `atexit` on the GPU
The `atexit` function controls registering functions to call at the end
of the program. This is difficult to do in general on the GPU because of
the lack of a real mutex implementation. We primarily provide this for
testing where we can explicitly restrict how the `atexit` registration
functions are called. So we simply create a passthrough Mutex to get
past the usage of it as per @sivachandra's suggestion.
Depends on D149225
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D149226
GitOrigin-RevId: dc9baac1a0148ce0c2b8afdc75e3e208597f79c9
5 files changed
