ProjectExplorer: Move makeInstallCommand()

... from Project to BuildSystem.

More direct and less use of Target::activeBuildConfiguration().

Change-Id: I148381d23be0f9ab0750ed1440e1b2b3e25aded0
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/projectexplorer/buildsteplist.cpp

@@ -196,7 +196,7 @@ void BuildStepList::moveStepUp(int position)
     emit stepMoved(position, position - 1);
 }
 
-BuildStep *BuildStepList::at(int position)
+BuildStep *BuildStepList::at(int position) const
 {
     return m_steps.at(position);
 }