ProjectExplorer: Replace virtual BuildStepConfigWidget::showWidget

... by a bool member.

One reason less for the need of custom derived classes, i.e. one
step forward to a setup where the then-generic config widget can be
created in BuildStepListWidget::init() and filled with aspect-
created subwidget, reducing the need of per-BuildStep boilerplate
similar to what was done in RunConfiguration recently.

Task-number: QTCREATORBUG-19985
Change-Id: I85d26bdb6b35d0d6715782214328a40eef87286e
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/plugins/android/androidpackageinstallationstep.cpp

@@ -128,6 +128,7 @@ namespace Internal {
 AndroidPackageInstallationStepWidget::AndroidPackageInstallationStepWidget(AndroidPackageInstallationStep *step)
     : m_step(step)
 {
+    setShowWidget(false);
 }
 
 QString AndroidPackageInstallationStepWidget::summaryText() const
@@ -140,11 +141,6 @@ QString AndroidPackageInstallationStepWidget::displayName() const
     return tr("Make install");
 }
 
-bool AndroidPackageInstallationStepWidget::showWidget() const
-{
-    return false;
-}
-
 //
 // AndroidPackageInstallationStepFactory
 //