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/ios/iosbuildstep.cpp

@@ -178,11 +178,6 @@ BuildStepConfigWidget *IosBuildStep::createConfigWidget()
     return new IosBuildStepConfigWidget(this);
 }
 
-bool IosBuildStep::immutable() const
-{
-    return false;
-}
-
 void IosBuildStep::setBaseArguments(const QStringList &args)
 {
     m_baseBuildArguments = args;

src/plugins/ios/iosbuildstep.h

@@ -52,7 +52,6 @@ public:
     void run(QFutureInterface<bool> &fi) override;
 
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
-    bool immutable() const override;
     void setBaseArguments(const QStringList &args);
     void setExtraArguments(const QStringList &extraArgs);
     QStringList baseArguments() const;

src/plugins/ios/iosdeploystep.cpp

@@ -59,6 +59,7 @@ const Core::Id IosDeployStep::Id("Qt4ProjectManager.IosDeployStep");
 IosDeployStep::IosDeployStep(BuildStepList *parent)
     : BuildStep(parent, Id)
 {
+    setImmutable(true);
     updateDisplayNames();
     connect(DeviceManager::instance(), &DeviceManager::updated,
             this, &IosDeployStep::updateDisplayNames);

src/plugins/ios/iosdeploystep.h

@@ -72,7 +72,6 @@ private:
 
     bool init(QList<const BuildStep *> &earlierSteps) override;
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
-    bool immutable() const override { return true; }
     bool runInGuiThread() const override { return true; }
     ProjectExplorer::IDevice::ConstPtr device() const;
     IosDevice::ConstPtr iosdevice() const;

src/plugins/ios/iosdsymbuildstep.cpp

@@ -197,11 +197,6 @@ BuildStepConfigWidget *IosDsymBuildStep::createConfigWidget()
     return new IosDsymBuildStepConfigWidget(this);
 }
 
-bool IosDsymBuildStep::immutable() const
-{
-    return false;
-}
-
 void IosDsymBuildStep::setArguments(const QStringList &args)
 {
     if (arguments() == args)

src/plugins/ios/iosdsymbuildstep.h

@@ -46,7 +46,6 @@ public:
     void run(QFutureInterface<bool> &fi) override;
 
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
-    bool immutable() const override;
     void setArguments(const QStringList &args);
     QStringList arguments() const;
     QStringList defaultArguments() const;