CMake Build: Ensure valid destinations for generated files

- Make the build system aware that empty_pch.c/.cpp are generated files
  to prevent invalid access from _add_pch_target.
- Force the creation of the translation output directory before copying
qm files into it.

Change-Id: Iaff5e5ebdbfec7e89a47d277d95f9dec760a5b6b
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

cmake/QtCreatorAPIInternal.cmake

@@ -349,6 +349,11 @@ function(enable_pch target)
         file(GENERATE
           OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/empty_pch.cpp
           CONTENT "/*empty file*/")
+        set_source_files_properties(
+            ${CMAKE_CURRENT_BINARY_DIR}/empty_pch.c
+            ${CMAKE_CURRENT_BINARY_DIR}/empty_pch.cpp
+            PROPERTIES GENERATED TRUE)
+
         _add_pch_target(QtCreatorPchGui
           "${PROJECT_SOURCE_DIR}/src/shared/qtcreator_gui_pch.h" Qt5::Widgets)
         _add_pch_target(QtCreatorPchConsole

cmake/QtCreatorTranslations.cmake

@@ -138,6 +138,8 @@ function(add_translation_targets file_prefix)
     add_custom_target("${_arg_ALL_QM_TARGET}" ALL COMMENT "Generate .qm-files")
   endif()
 
+  file(MAKE_DIRECTORY ${_arg_OUTPUT_DIRECTORY})
+
   foreach(l IN ITEMS ${_arg_LANGUAGES})
     set(_ts_file "${CMAKE_CURRENT_SOURCE_DIR}/${file_prefix}_${l}.ts")
     set(_qm_file "${_arg_OUTPUT_DIRECTORY}/${file_prefix}_${l}.qm")