message: check for submodule
diff: @@ -147,7 +147,7 @@ build-mpi: $(MPI_TARGETS)
  @echo '--- boost mpi bindings built ---'
  .PHONY: build
  -build: bin/stanc$(EXE) bin/stansummary$(EXE) bin/print$(EXE) bin/diagnose$(EXE) $(LIBSUNDIALS) $(MPI_TARGETS) $(CMDSTAN_MAIN_O)
  +build: check-submodule bin/stanc$(EXE) bin/stansummary$(EXE) bin/print$(EXE) bin/diagnose$(EXE) $(LIBSUNDIALS) $(MPI_TARGETS) $(CMDSTAN_MAIN_O)
  @echo ''
  @echo '--- CmdStan v$(CMDSTAN_VERSION) built ---'
  @@ -158,8 +158,10 @@ endif
  ##
  # Clean up.
  ##
  -.PHONY: clean clean-deps clean-manual clean-all
  +.PHONY: check-submodule clean clean-deps clean-manual clean-all
  +check-submodule:
  + @[ -e stan/src ] && : || echo "No stan/src folder found. Missing Stan submodule. Please run the following commands to fix \n git submodule init\n git submodule update --recursive\n"
  clean: clean-manual
  $(RM) -r test
  