This defines a WinMain() function that can be potentially problematic when it
isn't wanted. If we add back support for this library in the future, it should
be built separately from mingw32.lib and on demand.
Upstream commit dddccbc3ef50ac52bf00723fd2f68d98140aab80
* adds ucrtbase.def.in
* mingwex: replace mingw crt files with ucrt files
* adds missing mingw-w64 ucrt files
The rules that govern which set of files are included or excluded is
contained in the logic for tools/update_mingw.zig
