ProjectExplorer: Only warn about missing compilers

Not having a compiler defined in a kit is fine for e.g. Python
projects or QML projects. So only warn in that case.

Change-Id: Ic2bc30f8b70c804780b65e11915d1f231011a55c
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/projectexplorer/kitinformation.cpp

@@ -187,7 +187,7 @@ QList<Task> ToolChainKitInformation::validate(const Kit *k) const
 
     const QList<ToolChain*> tcList = toolChains(k);
     if (tcList.isEmpty()) {
-        result << Task(Task::Error, ToolChainKitInformation::msgNoToolChainInTarget(),
+        result << Task(Task::Warning, ToolChainKitInformation::msgNoToolChainInTarget(),
                        Utils::FileName(), -1, Core::Id(Constants::TASK_CATEGORY_BUILDSYSTEM));
     } else {
         QSet<Abi> targetAbis;