https://doc.rust-lang.org/rustc/platform-support/windows-gnullvm.html
> Windows targets similar to *-windows-gnu but using UCRT as the runtime and various LLVM tools/libraries instead of GCC/Binutils.
gnuのlibcじゃなくてUCRTって書かれてる
https://github.com/rust-lang/rust/blob/8a703520e80d87d4423c01f9d4fbc9e5f6533a02/compiler/rustc_target/src/spec/base/windows_gnullvm.rs#L19
```
let mingw_libs = &["-lmingw32", "-lmingwex", "-lmsvcrt", "-lkernel32", "-luser32"];
```
msvcrtって書かれてる
