os: add File.Chdir support

We should really be using syscall.Fchdir here, but this is a fix to get
Go 1.24 working.

src/os/file.go

@@ -318,6 +318,17 @@ func (f *File) Chmod(mode FileMode) (err error) {
 	return
 }
 
+// Chdir changes the current working directory to the file, which must be a
+// directory. If there is an error, it will be of type *PathError.
+func (f *File) Chdir() (err error) {
+	if f.handle == nil {
+		err = ErrClosed
+	} else {
+		err = f.chdir()
+	}
+	return
+}
+
 // LinkError records an error during a link or symlink or rename system call and
 // the paths that caused it.
 type LinkError struct {