Try to fix [make setup], again.

Makefile

@@ -45,7 +45,9 @@ all:
 
 .PHONY: setup
 setup:
-	opam install "dune>=2.0" "cppo" "pprint>=20200410" "seq" "odoc" "monolith"
+	opam install \
+	  "dune>=2.0" "cppo" "pprint>=20200410" "seq" "odoc" \
+	  "monolith" "ocamlfind"
 	make -C fuzz setup
 
 .PHONY: merlin

fuzz/Makefile

 SWITCH := 4.11.1+afl
 EXE := src/Main.exe
-# This line is somewhat problematic, as it assumes that monolith
-# is installed in the *current* switch, whatever it is.
+# This line is somewhat problematic, as it assumes that ocamlfind and
+# monolith are installed in the current switch, whatever it is.
 include $(shell ocamlfind query monolith)/Makefile.monolith