[spectec] Install opam dependencies automatically

Author: rossberg

spectec/Makefile

@@ -23,10 +23,15 @@ ROOTDIR = ..
 INTERPRETERDIR = $(ROOTDIR)/interpreter
 CLONEDIR = src/backend-interpreter/reference-interpreter
 CLONERM = dune-project jslib
+OPAMPACKAGES = zarith menhir
+
 
 .PHONY: exe
 
-exe: $(CLONEDIR)
+packages:
+	opam install $(OPAMPACKAGES)
+
+exe: $(CLONEDIR) packages
 	rm -f ./$(NAME)
 	dune build $(SRCDIR)/$(EXE)
 	ln -f $(OUTDIR)/$(EXE) ./$(NAME)