Check that chdir fails for non-utf8 paths

tests/compile-fail/chdir_invalid_path.rs

@@ -0,0 +1,11 @@
+// compile-flags: -Zmiri-disable-isolation
+
+extern {
+    pub fn chdir(dir: *const u8) -> i32;
+}
+
+fn main() {
+    let path = vec![0xc3u8, 0x28, 0];
+    // test that `chdir` errors with invalid utf-8 path
+    unsafe { chdir(path.as_ptr()) };  //~ ERROR is not a valid utf-8 string
+}