lib: fix clang compatibility / warnings

lib/tests/test-mu-maildir.cc

@@ -196,7 +196,7 @@ test_mu_maildir_flags_from_path(void)
 	}
 }
 
-static void
+[[maybe_unused]] static void
 assert_matches_regexp(const char* str, const char* rx)
 {
 	if (!g_regex_match_simple(rx, str, (GRegexCompileFlags)0, (GRegexMatchFlags)0)) {

lib/tests/test-parser.cc

@@ -32,7 +32,7 @@ using namespace Mu;
 struct Case {
 	const std::string expr;
 	const std::string expected;
-	WarningVec        warnings;
+	WarningVec        warnings{};
 };
 
 using CaseVec = std::vector<Case>;