qmake: Fix non-Xcode asset catalog handling for iOS simulator

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>

mkspecs/features/mac/asset_catalogs.prf

@@ -68,7 +68,7 @@
             $$asset_catalog_app_icon_arg \
             $$asset_catalog_launch_image_arg \
             --output-partial-info-plist $$shell_quote($$asset_catalog_compiler.target) \
-            --platform $${version_identifier} \
+            --platform $${platform_identifier} \
             --minimum-deployment-target $${deployment_target} \
             --compile $$shell_quote($$QMAKE_ASSET_CATALOGS_BUILD_PATH)
 

mkspecs/features/mac/default_post.prf

@@ -208,9 +208,11 @@ macx-xcode {
             contains(VALID_SIMULATOR_ARCHS, $$arch) {
                 sdk = $$simulator.sdk
                 version_identifier = $$simulator.deployment_identifier
+                platform_identifier = $$simulator.sdk
             } else {
                 sdk = $$device.sdk
                 version_identifier = $$device.deployment_identifier
+                platform_identifier = $$device.sdk
             }
 
             version_min_flags = \
@@ -237,9 +239,11 @@ macx-xcode {
     } else {
         simulator {
             version_identifier = $$simulator.deployment_identifier
+            platform_identifier = $$simulator.sdk
             sysroot_path  = $$xcodeSDKInfo(Path, $$simulator.sdk)
         } else {
             version_identifier = $$device.deployment_identifier
+            platform_identifier = $$device.sdk
             sysroot_path  = $$xcodeSDKInfo(Path, $$device.sdk)
         }
         version_min_flag = -m$${version_identifier}-version-min=$$deployment_target