Add workaround for QTBUG-35143

!!! Revert again ASAP !!!

Task-number: QTBUG-35143
Change-Id: I9eb724f07c7b6b49a7df0be4e1d4c76dac206af5
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/projectexplorer/buildconfiguration.cpp

@@ -250,8 +250,16 @@ Target *BuildConfiguration::target() const
 Utils::Environment BuildConfiguration::baseEnvironment() const
 {
     Utils::Environment result;
-    if (useSystemEnvironment())
+    if (useSystemEnvironment()) {
+#if 1
+        // workaround for QTBUG-35143
         result = Utils::Environment::systemEnvironment();
+        result.unset(QLatin1String("QSG_RENDER_LOOP"));
+#else
+        result = Utils::Environment::systemEnvironment();
+#endif
+    }
+
     target()->kit()->addToEnvironment(result);
     return result;
 }