Auto merge of #140154 - Berrysoft:cygwin-host, r=jieyouxu

Cygwin support in rustc

This PR builds host rustc targeting cygwin.

- [x] rust-lang/stacker#122
- [x] nagisa/rust_libloading#173
- [x] Detegr/rust-ctrlc#131
- [x] rust-random/getrandom#654
- [x] msys2/MSYS2-packages#5350
- [x] rust-lang/rust#140886
- [x] rust-lang/rust#140921
- [x] rust-lang/rust#140973

Currently supported:
* rustc
* rustdoc
* rustfmt
* clippy

Blocking:
* cargo: blocked by rust-lang/socket2#568
* rust-analyzer: needs `cargo update`, fixed upstream

```
$ rustc --version --verbose
rustc 1.88.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: x86_64-pc-cygwin
release: 1.88.0-dev
LLVM version: 20.1.4
```

Author: bors

src/shims/native_lib.rs

@@ -117,7 +117,12 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let mut info = std::mem::MaybeUninit::<libc::Dl_info>::uninit();
         unsafe {
             if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 {
-                if std::ffi::CStr::from_ptr(info.assume_init().dli_fname).to_str().unwrap()
+                let info = info.assume_init();
+                #[cfg(target_os = "cygwin")]
+                let fname_ptr = info.dli_fname.as_ptr();
+                #[cfg(not(target_os = "cygwin"))]
+                let fname_ptr = info.dli_fname;
+                if std::ffi::CStr::from_ptr(fname_ptr).to_str().unwrap()
                     != _lib_path.to_str().unwrap()
                 {
                     return None;