CMake: add compiled branding translations to build dir

- Copy the .qm files (compiled translations) into the build
   dir as part of the build process. This is independent of
   **installing** those same translations, but does allow
   the translations to be used by Calamares when run from the
   build dir for testing.

CMakeModules/CalamaresAddBrandingSubdirectory.cmake

@@ -107,7 +107,9 @@ function( calamares_add_branding_translations NAME )
     file( GLOB BRANDING_TRANSLATION_FILES RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "${SUBDIRECTORY}/lang/calamares-${NAME}_*.ts" )
     if ( BRANDING_TRANSLATION_FILES )
         qt5_add_translation( QM_FILES ${BRANDING_TRANSLATION_FILES} )
-        add_custom_target( branding-translation-${NAME} ALL DEPENDS ${QM_FILES} )
+        add_custom_target( branding-translation-${NAME} ALL DEPENDS ${QM_FILES}
+            COMMAND ${CMAKE_COMMAND} -E copy ${QM_FILES} ${CMAKE_CURRENT_BINARY_DIR}/${SUBDIRECTORY}/lang/
+        )
         install( FILES ${QM_FILES} DESTINATION ${BRANDING_COMPONENT_DESTINATION}/lang/ )
         list( LENGTH BRANDING_TRANSLATION_FILES _branding_count )
         message( "   ${Green}BRANDING_TRANSLATIONS:${ColorReset} ${_branding_count} language(s)" )