https://github.com/llvm/llvm-project/issues/159474

Another try of trying to land
https://github.com/llvm/llvm-project/pull/166382
- Fix some leftover tests checking for specific  errnos
- Guard errno checking tests to not run on the GPU

@michaelrj-google

https://github.com/llvm/llvm-project/issues/159474

Resubmitting https://github.com/llvm/llvm-project/pull/162876 with fixes
as it broke some buildbots:
 - Fix comparisons of integer expressions of different signedness
- Not check for specific errnos in tests, as they might not be available
on all platforms

[#159474](https://github.com/llvm/llvm-project/issues/159474)

- All printf variants set errno and consistently return -1 on error,
instead of returning various predefined error codes
- Return value overflow handling is added

Summary:
Currently we dispatch the writing mode off of a runtime enum passed in
by the constructor. This causes very unfortunate codegen for the GPU
targets where we get worst-case codegen because of the unused function
pointer for `sprintf`. Instead, this patch moves all of this to a
template so it can be masked out. This results in no dynamic stack and
uses 60 VGPRs instead of 117. It also compiles about 5x as fast.

This finishes the work from
https://github.com/llvm/llvm-project/pull/114453 by adding proxy headers
for `malloc`, `realloc`, `free` and `aligned_alloc`.

Summary:
This had some leftover references to the old namespace and didn't put
restrict on it.

[libc] Implement vasprintf and asprintf

---------

Co-authored-by: Izaak Schroeder <izaak.schroeder@gmail.com>