stylesheet: ignore QToolTip stylesheet on linux (and use custome one)

Gitlab: #515
Change-Id: I697cfc581497b9e3baf78f5e3212f7d832b863e9

ressources.qrc

@@ -8,6 +8,7 @@
         <file>images/icons/baseline-done-24px.svg</file>
         <file>images/icons/baseline-error_outline-24px.svg</file>
         <file>stylesheet.css</file>
+        <file>stylesheet.linux.css</file>
         <file>changelog.html</file>
         <file>images/ajax-loader.gif</file>
         <file>images/default_avatar_overlay.svg</file>

src/main.cpp

@@ -189,7 +189,11 @@ main(int argc, char* argv[])
     a.setFont(font);
 
 #ifndef DEBUG_STYLESHEET
+#ifdef Q_OS_LINUX
+    QFile file(":/stylesheet.linux.css");
+#else
     QFile file(":/stylesheet.css");
+#endif
     if (file.open(QIODevice::ReadOnly | QIODevice::Text)) {
         a.setStyleSheet(file.readAll());
         file.close();