If an iOS project was built with qmake using the Makefile generator
instead of the Xcode generator,
so -spec macx-ios-clang, and not -spec macx-xcode,
Asset catalog processing failed with an actool error like
Unknown platform: "ios-simulator"
This is because we used the deployment identifier (which is meant for
creation of the -mios-simulator-version-min flag) to pass a value
to actool's -platform option, rather than the sdk name.
Introduce a new variable called platform_identifier, which will be set
to the currently processed macOS/iOS sdk name (e.g. macosx,
iphonesimulator, iphoneos).
Use it when processing asset catalogs using the Makefile generator.
Relates to 9daeb6fe9d
Amends 5574aa986b
Pick-to: 6.3 6.4
Fixes: QTBUG-102053
Change-Id: Ic4ea3b9e11c21ae535d6544cbed3670f9db44e72
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
e38956e4f7