This starts pw_libc; with the intent to eventually have a basic subset
of libc implemented. These will be "CS 101" style implementations, that
aim for correctness and small code size.
The initial CL only adds tests against the system memset() function.
Change-Id: Icd681fff2bf5581c6d44e690bcb5f82a659a03a5
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/26201
Commit-Queue: Keir Mierle <keir@google.com>
Reviewed-by: Ewout van Bekkum <ewout@google.com>
