Check that the submodule exits.
Print an informative message if someone forgets to fetch the
submodule.
@@ -86,6 +86,13 @@ else ()
list(APPEND libobjc_C_SRCS eh_personality.c)
endif (WIN32)
+if (NOT EXISTS "${CMAKE_SOURCE_DIR}/third_party/robin-map/include/tsl/robin_map.h")
+ message(FATAL_ERROR "Git submodules not present, please run:\n\n"
+ " $ git submodule init && git submodule update\n\n"
+ "If you did not checkout via git, you will need to"
+ "fetch the submodule's contents from"
+ "https://github.com/Tessil/robin-map/")
+endif ()
# For release builds, we disable spamming the terminal with warnings about
# selector type mismatches
