[metadata] add missing MONO_ENTER/EXIT_GC_SAFE guards around access(2…

…) in is_file_writable (mono#7126)

mono/metadata/w32file-unix.c

@@ -893,6 +893,7 @@ static gboolean lock_while_writing = FALSE;
 static gboolean
 is_file_writable (struct stat *st, const gchar *path)
 {
+	gboolean ret;
 #if __APPLE__
 	// OS X Finder "locked" or `ls -lO` "uchg".
 	// This only covers one of several cases where an OS X file could be unwritable through special flags.
@@ -915,7 +916,10 @@ is_file_writable (struct stat *st, const gchar *path)
 	/* Fallback to using access(2). It's not ideal as it might not take into consideration euid/egid
 	 * but it's the only sane option we have on unix.
 	 */
-	return access (path, W_OK) == 0;
+	MONO_ENTER_GC_SAFE;
+	ret = access (path, W_OK) == 0;
+	MONO_EXIT_GC_SAFE;
+	return ret;
 }