CMake: Trigger cmake run *before* build when files changed

Make sure to run cmake *before* cmake --build when cmake files just
got saved. This helps e.g. when editing CMakeLists.txt files and the
hitting "Built" and "Save all" (or "Always save before build").

Task-number: QTCREATORBUG-16187
Change-Id: I16b1d02eb342a447003380946ce7a9d785476a0e
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildconfiguration.h

@@ -76,6 +76,7 @@ public:
     void maybeForceReparse();
     void resetData();
     bool persistCMakeState();
+    bool updateCMakeStateBeforeBuild();
     void runCMake();
     void clearCache();
 
@@ -111,7 +112,7 @@ private:
 
     mutable QList<CMakeConfigItem> m_completeConfigurationCache;
 
-    BuildDirManager *m_buildDirManager = nullptr;
+    BuildDirManager *const m_buildDirManager = nullptr;
 
     friend class CMakeBuildSettingsWidget;
     friend class CMakeProjectManager::CMakeProject;