[WASM] set _APP_RES_FOLDER if not defined to be able to specify directories of Resources (#2483)

* add AX_WASM_RES_FOLDER to specify dirs of Resources, Content/ by default

* use right var

* set _APP_RES_FOLDER if not defined

* Typo

* Remove spaces

Author: AlexandreK38

cmake/Modules/AXBuildHelpers.cmake

@@ -569,7 +569,9 @@ macro (ax_setup_app_props app_name)
         # string(APPEND EMSCRIPTEN_LINK_FLAGS " -s SEPARATE_DWARF_URL=https://xxx:8080/axmolwasm/axmolwasm/build/HelloLua.debug.wasm")
         # string(APPEND EMSCRIPTEN_LINK_FLAGS " -gseparate-dwarf=HelloLua.debug.wasm")
 
-        set(_APP_RES_FOLDER "${_APP_SOURCE_DIR}/Content")
+        if (NOT DEFINED _APP_RES_FOLDER)
+            set(_APP_RES_FOLDER "${_APP_SOURCE_DIR}/Content")
+        endif()
         foreach(FOLDER IN LISTS _APP_RES_FOLDER)
             string(APPEND EMSCRIPTEN_LINK_FLAGS " --preload-file ${FOLDER}/@/")
         endforeach()