Let CRT take care of the entry point for wWinMain if libc is linked

Fixes #7852

Before, the modified test would fail with:

```
error: lld-link: undefined symbol: wWinMain
    note: referenced by C:\Users\Ryan\Programming\Zig\zig-x86_64-windows-0.15.1\lib\libc\mingw\crt\crtexewin.c:66
    note:               libmingw32.lib(ucrtexewin.obj):(wmain)
```
b31a03f134Ryan Liptak committed on 11/9/2025, 1:11:12 AMparentbe4eaed
4 files changedLine totals unavailable