[autotests] Force XKB_DEFAULT_RULES to evdev in ModifierOnlyShortcutsTest

This is an idea to fix the failing test on FreeBSD (see T6624). For
Linux this does not change anything.

autotests/integration/modifier_only_shortcut_test.cpp

@@ -97,6 +97,7 @@ void ModifierOnlyShortcutTest::initTestCase()
 
     kwinApp()->setConfig(KSharedConfig::openConfig(QString(), KConfig::SimpleConfig));
     qputenv("KWIN_XKB_DEFAULT_KEYMAP", "1");
+    qputenv("XKB_DEFAULT_RULES", "evdev");
 
     kwinApp()->start();
     QVERIFY(workspaceCreatedSpy.wait());