CMake: Add helper method to find the default build target for a BuildStep

Add a helper method to find the default build target for a CMakeBuildStep
based on the BuildStepList the step is part of. Use all/install/clean
targets as appropriate.

This change has been cherry-picked from master branch:
8b9821440d

Change-Id: Idc0c5fae7dfd255039b87ace77c02688cdd76e8f
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildstep.cpp

@@ -91,14 +91,8 @@ CMakeBuildStep::CMakeBuildStep(BuildStepList *bsl) :
     }
 
     // Set a good default build target:
-    if (m_buildTarget.isEmpty()) {
-        if (bsl->id() == ProjectExplorer::Constants::BUILDSTEPS_CLEAN)
-            setBuildTarget(cleanTarget());
-        else if (bsl->id() == ProjectExplorer::Constants::BUILDSTEPS_DEPLOY)
-            setBuildTarget(installTarget());
-        else
-            setBuildTarget(allTarget());
-    }
+    if (m_buildTarget.isEmpty())
+        setBuildTarget(defaultBuildTarget());
 
     connect(target(), &Target::kitChanged, this, &CMakeBuildStep::cmakeCommandChanged);
     connect(project(), &Project::parsingFinished,
@@ -277,6 +271,17 @@ BuildStepConfigWidget *CMakeBuildStep::createConfigWidget()
     return new CMakeBuildStepConfigWidget(this);
 }
 
+QString CMakeBuildStep::defaultBuildTarget() const
+{
+    const ProjectConfiguration *const pc = qobject_cast<ProjectConfiguration *>(parent());
+    const Core::Id parentId = pc ? pc->id() : Core::Id();
+    if (parentId == ProjectExplorer::Constants::BUILDSTEPS_CLEAN)
+        return cleanTarget();
+    if (parentId == ProjectExplorer::Constants::BUILDSTEPS_DEPLOY)
+        return installTarget();
+    return allTarget();
+}
+
 void CMakeBuildStep::stdOutput(const QString &line)
 {
     if (m_percentProgress.indexIn(line) != -1) {

src/plugins/cmakeprojectmanager/cmakebuildstep.h

@@ -98,6 +98,8 @@ private:
     void doRun() override;
     ProjectExplorer::BuildStepConfigWidget *createConfigWidget() override;
 
+    QString defaultBuildTarget() const;
+
     void runImpl();
     void handleProjectWasParsed(bool success);