Install data files from git submodule

.gitmodules

@@ -8,3 +8,6 @@
 [submodule "thirdparty/Spice"]
 	path = thirdparty/Spice
 	url = https://github.com/OpenSpace/Spice
+[submodule "content"]
+	path = content
+	url = https://github.com/CelestiaProject/CelestiaContent.git

CMakeLists.txt

@@ -33,6 +33,7 @@ option(FAST_MATH      "Build with unsafe fast-math compiller option (Default: of
 option(ENABLE_TTF     "Use TrueType fonts instead of TXF (Default: off)" OFF)
 option(ENABLE_TESTS   "Enable unit tests? (Default: off)" OFF)
 option(ENABLE_GLEW    "Use GLEW instead of libepoxy? (Default: on)" ON)
+option(ENABLE_DATA    "Install data from content submodule? (Default: off)" OFF)
 
 if(NOT CMAKE_BUILD_TYPE)
   set(CMAKE_BUILD_TYPE "Release" CACHE STRING "Build type." FORCE)
@@ -354,6 +355,10 @@ add_subdirectory(locale)
 add_subdirectory(scripts)
 add_subdirectory(shaders)
 
+if(ENABLE_DATA)
+  add_subdirectory(content)
+endif()
+
 if(ENABLE_TESTS)
   enable_testing()
   add_subdirectory(test)

content

@@ -0,0 +1 @@
+Subproject commit 7012d92a37b240a53ce8d445907d4b2d32433e5a