CMakePM: Add support for qtc_runnable feature

This will allow for the Qt Creator's CMake build only qtcreator
target to be selected as runnable.

Similar to qmake's qtc_runnable or Qbs's qtcRunnable features.

Fixes: QTCREATORBUG-25908
Change-Id: I6416873d0ad9cfec4960d98fc4b289ec98cc58b1
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildtarget.h

@@ -54,6 +54,7 @@ public:
     Utils::FilePath executable; // TODO: rename to output?
     TargetType targetType = UtilityType;
     bool linksToQtGui = false;
+    bool qtcRunnable = true;
     Utils::FilePath workingDirectory;
     Utils::FilePath sourceDirectory;
     Utils::FilePath makeCommand;