QMake: Remove unnecessary build dir changed

Previously every time a qmake project was built, the
"buildDirectoryChanged()" was emitted, leading to a complete
reparse of the project file, tests, qml files and qml imports.

To keep "QmakeBuildConfiguration::updateProblemLabel" be called,
we re-introduce the "buildDirectoryInitialized" signal.

Task-number: QTCREATORBUG-27785
Change-Id: I32d881eacb8cf26050c33da643c74c2cab4dc22d
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/projectexplorer/buildconfiguration.h

@@ -116,6 +116,7 @@ public:
 
 signals:
     void environmentChanged();
+    void buildDirectoryInitialized();
     void buildDirectoryChanged();
     void enabledChanged();
     void buildTypeChanged();

src/plugins/qmakeprojectmanager/qmakebuildconfiguration.cpp

@@ -153,6 +153,8 @@ QmakeBuildConfiguration::QmakeBuildConfiguration(Target *target, Id id)
     });
 
     buildDirectoryAspect()->allowInSourceBuilds(target->project()->projectDirectory());
+    connect(this, &BuildConfiguration::buildDirectoryInitialized,
+            this, &QmakeBuildConfiguration::updateProblemLabel);
     connect(this, &BuildConfiguration::buildDirectoryChanged,
             this, &QmakeBuildConfiguration::updateProblemLabel);
     connect(this, &QmakeBuildConfiguration::qmakeBuildConfigurationChanged,

src/plugins/qmakeprojectmanager/qmakestep.cpp

@@ -306,7 +306,7 @@ bool QMakeStep::processSucceeded(int exitCode, QProcess::ExitStatus status)
     bool result = AbstractProcessStep::processSucceeded(exitCode, status);
     if (!result)
         m_needToRunQMake = true;
-    emit buildConfiguration()->buildDirectoryChanged();
+    emit buildConfiguration()->buildDirectoryInitialized();
     return result;
 }