add makefile target for zkevm.gob

This adds a new target for constructing a `zkevm.gob` using `go-corset`.
For now, we use `zkevm.gob` until things have stablised and we can
return to the `zkevm.bin` format as before.

Makefile

@@ -1,4 +1,5 @@
 CORSET ?= corset
+GO_CORSET ?= go-corset
 
 HUB_COLUMNS :=  $(wildcard hub/columns/*lisp)
 
@@ -171,6 +172,9 @@ define.go: ${ZKEVM_MODULES}
 zkevm.bin: ${ZKEVM_MODULES}
 	${CORSET} compile -vv -o $@ ${ZKEVM_MODULES}
 
+zkevm.gob: ${ZKEVM_MODULES}
+	${GO_CORSET} compile -o $@ ${ZKEVM_MODULES}
+
 
 ZKEVM_MODULES_FOR_REFERENCE_TESTS := ${ALU} \
 				     ${BIN} \