checkout test: check getcwd return value

tests/checkout/index.c

@@ -145,7 +145,7 @@ void test_checkout_index__honor_coresymlinks_default(void)
 
 	const char *url = git_repository_path(g_repo);
 
-	getcwd(cwd, sizeof(cwd));
+	cl_assert(getcwd(cwd, sizeof(cwd)) != NULL);
 	cl_assert_equal_i(0, p_mkdir("readonly", 0555)); // Read-only directory
 	cl_assert_equal_i(0, chdir("readonly"));
 	cl_git_pass(git_repository_init(&repo, "../symlink.git", true));