tests: skip some slow tests when valgrinding

lib/mu-indexer.cc

@@ -489,6 +489,8 @@ test_index_basic()
 	g_assert_cmpuint(prog.updated,==, 0);
 	g_assert_cmpuint(prog.removed,==, 0);
 
+	mu_test_skip_valgrind_return();
+
 	Indexer::Config conf{};
 	conf.ignore_noupdate = true;
 
@@ -540,6 +542,8 @@ test_index_lazy()
 {
 	allow_warnings();
 
+	mu_test_skip_valgrind_return();
+
 	TempDir tdir;
 	auto store = Store::make_new(tdir.path(), MU_TESTMAILDIR2);
 	assert_valid_result(store);

lib/tests/test-mu-store.cc

@@ -492,13 +492,15 @@ Yes, that would be excellent.
 }
 
 static void
-test_store_circular_symlink(void)
+test_store_circular_symlink()
 {
 	allow_warnings();
 
 	g_test_bug("2517");
 	g_test_bug("2832");
 
+	mu_test_skip_valgrind_return();
+
 	auto testhome{unwrap(make_temp_dir())};
 	auto dbpath{runtime_path(RuntimePath::XapianDb, testhome)};
 
@@ -513,6 +515,7 @@ test_store_circular_symlink(void)
 	auto&& store = unwrap(Store::make_new(dbpath, testmdir));
 	store.indexer().start({});
 	size_t n{};
+
 	while (store.indexer().is_running()) {
 		std::this_thread::sleep_for(100ms);
 		// 5 sec should be enough, even on the slowest supported systems..