🦫 mmap: move away from calling Fd() directly on windows

Starting from Go 1.25, Fd() on windows will have the same side effect of turning the file into blocking mode. We don't open the file in non-blocking mode, but we also don't like the new side effect. Nonetheless, it's never a bad thing to unify the implementations.

Author: database64128

mmap/mmap_windows.go

@@ -8,7 +8,19 @@ import (
 )
 
 func readFile(f *os.File, size uintptr) (addr unsafe.Pointer, close func() error, err error) {
-	handle, err := windows.CreateFileMapping(windows.Handle(f.Fd()), nil, windows.PAGE_READONLY, 0, 0, nil)
+	rawConn, err := f.SyscallConn()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var handle windows.Handle
+
+	if cerr := rawConn.Control(func(fd uintptr) {
+		handle, err = windows.CreateFileMapping(windows.Handle(fd), nil, windows.PAGE_READONLY, 0, 0, nil)
+	}); cerr != nil {
+		return nil, nil, cerr
+	}
+
 	if err != nil {
 		return nil, nil, os.NewSyscallError("CreateFileMappingW", err)
 	}