Make the build parser for custom build steps depend on the toolchain

The API addtition to BuildConfiguration of knowing of the default parser
is rather strange, but a necessary evil for this.

Reviewed-By: Thorbjorn

Task-Nr: QTCREATORBUG-514

src/plugins/genericprojectmanager/genericbuildconfiguration.h

@@ -57,6 +57,8 @@ public:
 
     QVariantMap toMap() const;
 
+    ProjectExplorer::IOutputParser *createOutputParser() const;
+
 protected:
     GenericBuildConfiguration(GenericTarget *parent, GenericBuildConfiguration *source);
     GenericBuildConfiguration(GenericTarget *parent, const QString &id);