ToolChainFactory: Add support for different languages

* Add a pure virtual method to get supportedLanguges with

Change-Id: Ida4445ca045c90fb9f7656a661af83e5b6801b30
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/projectexplorer/customtoolchain.cpp

@@ -432,6 +432,11 @@ CustomToolChainFactory::CustomToolChainFactory()
     setDisplayName(tr("Custom"));
 }
 
+QSet<ToolChain::Language> CustomToolChainFactory::supportedLanguages() const
+{
+    return { ToolChain::Language::Cxx };
+}
+
 bool CustomToolChainFactory::canCreate()
 {
     return true;