macOS: Don't link to debug versions of frameworks unless requested

The failure mode of this behavior is worse than the surprises that the
non-explicit library dependency chain has, so it should be opt-in.

This reverts back to the behavior in Qt 5.11, but lets our tests
opt in to the feature.

Fixes: QTBUG-71724
Change-Id: Iede11f02d978b637324ddf71d29e7c99fe3ee99f
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

mkspecs/features/qt.prf

@@ -231,7 +231,7 @@ for(ever) {
         !isEmpty(MODULE_MODULE) {
             contains(MODULE_CONFIG, lib_bundle) {
                 framework = $$MODULE_MODULE
-                qtConfig(debug_and_release):!macx-xcode {
+                qtConfig(debug_and_release):qt_link_suffixed_framework:!macx-xcode {
                     platform_target_suffix = $$qtPlatformTargetSuffix()
                     !isEmpty(platform_target_suffix): \
                         # The -framework linker argument supports a name[,suffix] version,

mkspecs/features/testcase.prf

@@ -21,6 +21,9 @@ testcase_lowdpi {
     }
 }
 
+# Make sure we explicitly link to the debug version of the Qt libraries if needed
+macos: CONFIG += qt_link_suffixed_framework
+
 benchmark: type = benchmark
 else: type = check