cmake: fetch submodule if not available

CMakeLists.txt

@@ -53,9 +53,27 @@ set(DOXYGEN_USE_MATHJAX YES)
 set(CMAKE_VERBOSE_MAKEFILE TRUE)
 
 # JRL-cmakemodule setup
-include(cmake/base.cmake)
-include(cmake/ide.cmake)
-include(cmake/apple.cmake)
+set(JRL_CMAKE_MODULES "${CMAKE_CURRENT_LIST_DIR}/cmake")
+if(NOT EXISTS "${CMAKE_SOURCE_DIR}/cmake/base.cmake")
+  if(${CMAKE_VERSION} VERSION_LESS "3.14.0")
+    message(
+      FATAL_ERROR
+        "\nPlease run the following command first:\ngit submodule update --init\n"
+    )
+  else()
+    message(STATUS "JRL cmakemodules not found. Let's fetch it.")
+    include(FetchContent)
+    FetchContent_Declare(
+      "jrl-cmakemodules"
+      GIT_REPOSITORY "https://github.com/jrl-umi3218/jrl-cmakemodules.git")
+    FetchContent_MakeAvailable("jrl-cmakemodules")
+    FetchContent_GetProperties("jrl-cmakemodules" SOURCE_DIR JRL_CMAKE_MODULES)
+  endif()
+endif()
+
+include("${JRL_CMAKE_MODULES}/base.cmake")
+include("${JRL_CMAKE_MODULES}/ide.cmake")
+include("${JRL_CMAKE_MODULES}/apple.cmake")
 
 # Handle APPLE Cmake policy
 if(APPLE)