[cleanup] Actually I have found that a cleaner solution is just to upgrade fflate.

https://github.com/101arrowz/fflate/issues/17

dune

@@ -9,7 +9,7 @@
   (package coq))
  (action
   (progn
-   (run node --experimental-worker %{dep:cli.js} %{dep:coq-jslib/metadata/coq-pkgs.json}
+   (run node %{dep:cli.js} %{dep:coq-jslib/metadata/coq-pkgs.json}
              --rootdir %{env:COQBUILDDIR_REL=.} --nostdlib))))
 
 (rule

etc/docker/Makefile

@@ -9,6 +9,8 @@ export NJOBS ?= 4
 ARGS = --build-arg REPO --build-arg BRANCH --build-arg NJOBS
 # --progress plain --no-cache=true
 
+EXISTING_IMAGES = ${shell docker images --filter=reference="jscoq:*" --format '{{.Repository}}:{{.Tag}}'}
+
 build:
 	docker build . --target opam         $(ARGS)  -t jscoq:opam
 	docker build . --target jscoq-prereq $(ARGS)  -t jscoq:prereq
@@ -16,12 +18,19 @@ build:
 	docker build . --target jscoq-addons $(ARGS)  -t jscoq:addons
 
 dist:
+	rm -rf ./dist
 	docker run --name jscoq-get-dist jscoq:addons \
 		sh -c 'mkdir -p dist && cp _build/jscoq+64bit/*.tgz dist'
 	docker cp jscoq-get-dist:/root/jscoq/dist .
 	docker cp jscoq-get-dist:/root/jscoq-addons/dist .
 	docker rm jscoq-get-dist
 
+clean:
+	docker image rm ${filter-out jscoq:opam jscoq:prereq, $(EXISTING_IMAGES)}
+
+clean-slate:
+	docker image rm $(EXISTING_IMAGES)
+
 serve:
 	docker run --publish 8080:8080 --rm -it jscoq \
 		npx static-server -p 8080 _build/dist

package.json

@@ -11,7 +11,7 @@
     "bootstrap": "^3.4.1",
     "codemirror": "^5.49.2",
     "commander": "^5.0.0",
-    "fflate-unzip": "^0.3.6-0",
+    "fflate-unzip": "^0.6.0",
     "find": "^0.3.0",
     "glob": "^7.1.3",
     "jquery": "^3.5.1",