Pull submodules with cmake

CMakeLists.txt

@@ -16,6 +16,25 @@ add_definitions(
 set(CMAKE_BUILD_TYPE Debug)
 # set(CMAKE_BUILD_TYPE Release)
 
+
+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 update --init --recursive
+                        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+                        RESULT_VARIABLE GIT_SUBMOD_RESULT)
+        if(NOT GIT_SUBMOD_RESULT EQUAL "0")
+            message(FATAL_ERROR "git submodule update --init --recursive failed with ${GIT_SUBMOD_RESULT}, please checkout submodules")
+        endif()
+    endif()
+endif()
+
+if(NOT EXISTS "${PROJECT_SOURCE_DIR}/third-party/uuid_v4/CMakeLists.txt")
+    message(FATAL_ERROR "The submodules were not downloaded! GIT_SUBMODULE was turned off or failed. Please update submodules and try again.")
+endif()
+
 # internal libraries
 add_subdirectory(app)
 add_subdirectory(src/Camera)