unit_tests to init git modules

unit_tests/Makefile

@@ -3,6 +3,16 @@
 # NOTE: Can be overridden externally.
 #
 
+
+ifeq ("$(wildcard googletest/LICENSE)","")
+$(info Invoking "git submodule update --init")
+$(shell git submodule update --init)
+$(info Invoked "git submodule update --init")
+# make is not happy about newly checked out module for some reason but next invocation would work
+$(error Please run 'make' again. Please make sure you have 'git' command in PATH)
+endif
+
+
 PROJECT_DIR = ../firmware
 
 # Compiler options here.