ProjectExplorer: Make BuildStep::immutable use a data member

Default to false, remove all no-op reimplementations.

And rename the getter to isImmutable according to the rules.

Change-Id: I8cce79d88fb59badfa1cffcf30a46f7ff3b09e8b
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/android/androidbuildapkstep.cpp

@@ -129,6 +129,7 @@ AndroidBuildApkStep::AndroidBuildApkStep(BuildStepList *parent)
 {
     //: AndroidBuildApkStep default display name
     setDefaultDisplayName(tr("Build Android APK"));
+    setImmutable(true);
 }
 
 bool AndroidBuildApkStep::init(QList<const BuildStep *> &earlierSteps)

src/plugins/android/androidbuildapkstep.h

@@ -77,7 +77,6 @@ private:
 
     bool init(QList<const BuildStep *> &earlierSteps) override;
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
-    bool immutable() const override { return true; }
     void processStarted() override;
     void processFinished(int exitCode, QProcess::ExitStatus status) override;
     bool verifyKeystorePassword();

src/plugins/android/androiddeployqtstep.cpp

@@ -92,6 +92,7 @@ AndroidDeployQtStepFactory::AndroidDeployQtStepFactory()
 AndroidDeployQtStep::AndroidDeployQtStep(ProjectExplorer::BuildStepList *parent)
     : ProjectExplorer::BuildStep(parent, Id)
 {
+    setImmutable(true);
     m_uninstallPreviousPackage = QtSupport::QtKitInformation::qtVersion(target()->kit())->qtVersion() < QtSupport::QtVersionNumber(5, 4, 0);
 
     //: AndroidDeployQtStep default display name

src/plugins/android/androiddeployqtstep.h

@@ -97,7 +97,6 @@ private:
     void slotSetSerialNumber(const QString &serialNumber);
 
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
-    bool immutable() const override { return true; }
 
     void processReadyReadStdOutput(DeployErrorCode &errorCode);
     void stdOutput(const QString &line);

src/plugins/android/androidpackageinstallationstep.cpp

@@ -53,6 +53,7 @@ AndroidPackageInstallationStep::AndroidPackageInstallationStep(BuildStepList *bs
     setDefaultDisplayName(name);
     setDisplayName(name);
     setWidgetExpandedByDefault(false);
+    setImmutable(true);
 }
 
 bool AndroidPackageInstallationStep::init(QList<const BuildStep *> &earlierSteps)
@@ -115,11 +116,6 @@ BuildStepConfigWidget *AndroidPackageInstallationStep::createConfigWidget()
 }
 
 
-bool AndroidPackageInstallationStep::immutable() const
-{
-    return true;
-}
-
 //
 // AndroidPackageInstallationStepWidget
 //

src/plugins/android/androidpackageinstallationstep.h

@@ -43,7 +43,6 @@ public:
     bool init(QList<const BuildStep *> &earlierSteps) override;
 
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
-    bool immutable() const override;
 
     void run(QFutureInterface<bool> &fi) override;