Meson: Fix tool argument UI setup

The line edit needs to be initialized with the stored arguments.

Fixes: QTCREATORBUG-29351
Change-Id: I9c4e0eed05a5c00520aebf1c6c4ea3cf17ef17df
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/mesonprojectmanager/ninjabuildstep.cpp

@@ -59,6 +59,7 @@ QWidget *NinjaBuildStep::createConfigWidget()
     buildTargetsList->setFrameShadow(QFrame::Raised);
 
     auto toolArguments = new QLineEdit(widget);
+    toolArguments->setText(m_commandArgs);
 
     auto wrapper = Core::ItemViewFind::createSearchableWrapper(buildTargetsList,
                                                                Core::ItemViewFind::LightColored);