Pin stackage dependencies

This should address some of the caching issues we run into.

As mentioned in this GitHub issue:
tweag/rules_haskell#1293, there are issues
with `stack` running intermittently locally, and with caching not really
working on any of the CI systems we use. It looks like the
`stack_snapshot_json` argument should help with that.

After working with it for a little while, it looks like we consistently
get sub-second `bazel test //...` when it should be a no-op! This is the
behavior we wanted, and it's here!

We'll have to see how this plays out on CI.

We also add a rule in the `Makefile` to help with regenerating that
pinned file when we make changes.

Makefile

@@ -9,6 +9,9 @@ VERSION_BAZEL := 2.2.0
 VERSION_IBAZEL := 0.12.3
 
 PACKAGE_JSON := package.json
+STACKAGE_SNAPSHOT := snapshot.yaml
+STACKAGE_SNAPSHOT_PINNED := stackage_snapshot.json
+WORKSPACE := WORKSPACE.bazel
 
 # Based on https://stackoverflow.com/a/12099167/1549047.
 ifeq ($(OS),Windows_NT)
@@ -49,11 +52,15 @@ $(IBAZEL): | $(BUILDDIR)
 	@touch $@
 	$(IBAZEL) version
 
-$(PACKAGE_JSON): $(BAZEL)
+$(PACKAGE_JSON): $(BAZEL) $(STACKAGE_SNAPSHOT_PINNED)
 	$(info Generating $@ file)
 	$(BAZEL) build //ci/npm:package.json
 	cp $(BAZEL_BINDIR)/ci/npm/package.json $@
 
+$(STACKAGE_SNAPSHOT_PINNED): $(BAZEL) $(STACKAGE_SNAPSHOT) $(WORKSPACE)
+	$(info Generating $@ file)
+	$(BAZEL) run @stackage-unpinned//:pin
+
 .PHONY: clean
 clean:
 	$(info Removing $(BUILDDIR))
@@ -63,7 +70,7 @@ clean:
 	@git clean -X --force $(BINDIR)/*
 
 .PHONY: coverage
-coverage: $(BAZEL)
+coverage: $(BAZEL) $(STACKAGE_SNAPSHOT_PINNED)
 	$(BAZEL) coverage $(BAZEL_CONFIG) //...
 
 .PHONY: format
@@ -76,18 +83,21 @@ format: $(BAZEL)
 	$(BAZEL) run $(BAZEL_CONFIG) //pkg/cst:format-ormolu
 
 .PHONY: lint
-lint: $(BAZEL)
+lint: $(BAZEL) $(STACKAGE_SNAPSHOT_PINNED)
 	$(BAZEL) test $(BAZEL_CONFIG) //:lint
 
 .PHONY: npm-publish
 npm-publish: $(PACKAGE_JSON)
 	$(info Publishing to npm)
 	npm publish
 
+.PHONY: pin-stackage
+pin-stackage: $(STACKAGE_SNAPSHOT_PINNED)
+
 .PHONY: test
-test: $(BAZEL)
+test: $(BAZEL) $(STACKAGE_SNAPSHOT_PINNED)
 	$(BAZEL) test $(BAZEL_CONFIG) //...
 
 .PHONY: watch
-watch: $(IBAZEL)
+watch: $(IBAZEL) $(STACKAGE_SNAPSHOT_PINNED)
 	$(IBAZEL) test $(BAZEL_CONFIG) //...

WORKSPACE.bazel

@@ -198,6 +198,7 @@ stack_snapshot(
         "semigroups",
         "text",
     ],
+    stack_snapshot_json = "//:stackage_snapshot.json",
     tools = [
         "@alex",
         "@happy",