CMake: Fix GCC warning

cmakeparser.cpp: In member function ‘virtual ProjectExplorer::IOutputParser::Status CMakeProjectManager::CMakeParser::doHandleLine(const QString&, Utils::OutputFormat)’:
cmakeparser.cpp:143:1: warning: control reaches end of non-void function [-Wreturn-type]
  143 | }
      | ^

Change-Id: I876e096d965444b9b72ef0dddcbc52e7a201eb02
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/cmakeprojectmanager/cmakeparser.cpp

@@ -140,6 +140,7 @@ IOutputParser::Status CMakeParser::doHandleLine(const QString &line, OutputForma
         doFlush();
         return Status::Done;
     }
+    return Status::NotHandled;
 }
 
 void CMakeParser::doFlush()