Ensure QtWebEngineProcess is built in release mode

If debug_and_release is set then QtWebEngineProcess should be built in
release mode as it is a separate process and when it is deployed later it
will be in the right mode already.

Change-Id: I377baa20f01b70db91a7a1cec5f1014b44780546
Reviewed-by: Michael Brüning <michael.bruning@theqtcompany.com>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>

src/process/process.pro

 TARGET = $$QTWEBENGINEPROCESS_NAME
 TEMPLATE = app
-
+!build_pass:contains(QT_CONFIG, debug_and_release):contains(QT_CONFIG, build_all): CONFIG += release
 # Needed to set LSUIElement=1
 QMAKE_INFO_PLIST = Info_mac.plist