ProjectExplorer: Fix name not queried on adding new build configuration

BuildSettingsWidget::createConfiguration() works with a BuildInfo
object borrowed from an IBuildConfigurationFactory, and uses it to create
a new build configuration.

The original BuildInfo object should not be permanently changed, as it's
only used here for creating the new build configuration.

Ideally, it should work on a clone of the buildinfo/factory, but that
would require adding and implementing a polymorphic clone method
for either class.

This commit works around this problem by restoring the original
displayName of the buildinfo after use.

Task-number: QTCREATORBUG-12955
Change-Id: Iccf2123c4377a39396860a1cfaa817a98dacebd4
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/projectexplorer/buildsettingspropertiespage.cpp

@@ -238,6 +238,7 @@ void BuildSettingsWidget::createConfiguration()
 {
     QAction *action = qobject_cast<QAction *>(sender());
     BuildInfo *info = static_cast<BuildInfo *>(action->data().value<void*>());
+    QString originalDisplayName = info->displayName;
 
     if (info->displayName.isEmpty()) {
         bool ok = false;
@@ -256,6 +257,7 @@ void BuildSettingsWidget::createConfiguration()
 
     m_target->addBuildConfiguration(bc);
     m_target->setActiveBuildConfiguration(bc);
+    info->displayName = originalDisplayName;
 }
 
 void BuildSettingsWidget::cloneConfiguration()