CMakeLists: install Qt translations to macOS bundle

Closes #731.

CMakeLists.txt

@@ -301,8 +301,20 @@ endif(WIN32)
 # Packaging
 
 if(APPLE)
+    execute_process(
+        COMMAND "${${Qt}_BinDir}/qmake" -query QT_INSTALL_TRANSLATIONS
+        OUTPUT_VARIABLE _qt_translations_dir
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+        COMMAND_ERROR_IS_FATAL ANY
+    )
     set(MACDEPLOYQT_ARGS ${PROJECT_NAME}.app -dmg -qmldir="${QML_DIR}" -verbose=${DEPLOY_VERBOSITY})
     add_custom_target(image
+        COMMAND ${CMAKE_COMMAND} -E make_directory ${PROJECT_NAME}.app/Contents/Translations
+        COMMAND ${CMAKE_COMMAND} -E copy
+            "${_qt_translations_dir}/qtbase_*.qm"
+            "${_qt_translations_dir}/qtdeclarative_*.qm"
+            "${_qt_translations_dir}/qtmultimedia_*.qm"
+            ${PROJECT_NAME}.app/Contents/Translations
         COMMAND "${${Qt}_BinDir}/macdeployqt" ${MACDEPLOYQT_ARGS}
         DEPENDS ${PROJECT_NAME}
         WORKING_DIRECTORY ${PROJECT_BINARY_DIR}