[libc][wchar] implement wcspbrk

[nickdesaulniers]

In order to build cxxabi, we need wcspbrk. We also need wcstombs wired up to be able to test this.

See also #121183.

[llvmbot]

@llvm/issue-subscribers-libc

Author: Nick Desaulniers (nickdesaulniers)

In order to build cxxabi, we need wcspbrk. We also need wcstombs wired up to be able to test this.

See also #121183.

[michaelrj-google]

Described in C23 (page 453): https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf#page=453

wcspbrk finds the first occurrence of any character of s2 in wide string s1.

Here's a checklist for what you'll need to do for this:

• Add the implementation of wcspbrk in /src/wchar
• Add tests for wcspbrk in /test/src/wchar
• Add wcspbrk to entrypoints.txt for at least x86_64 and whatever you're building on
• Add wcspbrk to include/wchar.yaml

(Reserved for specific assignee)

[uzairnawaz]

I'll work on this!

[michaelrj-google]

completed in #142040