Run git submodule --sync in cmake

CMakeLists.txt

@@ -40,7 +40,16 @@ if(GIT_FOUND AND EXISTS "${PROJECT_SOURCE_DIR}/.git")
   # Update submodules as needed
   option(GIT_SUBMODULE "Check submodules during build" ON)
   if(GIT_SUBMODULE)
-    message(STATUS "Submodule update")
+    execute_process(
+      COMMAND ${GIT_EXECUTABLE} submodule sync --recursive
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+      RESULT_VARIABLE GIT_SUBMOD_SYNC_RESULT)
+    if(NOT GIT_SUBMOD_SYNC_RESULT EQUAL "0")
+      message(
+        FATAL_ERROR
+          "git submodule sync failed with ${GIT_SUBMOD_SYNC_RESULT}, please checkout submodules"
+      )
+    endif()
     execute_process(
       COMMAND ${GIT_EXECUTABLE} submodule update --init --recursive --checkout
       WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}