Merge pull request #3729 from filecoin-project/fix/statediff-ci

ci: fix statediff build; make optional.

.circleci/config.yml

@@ -231,11 +231,11 @@ jobs:
       - run:
           name: install statediff globally
           command: |
+            ## statediff is optional; we succeed even if compilation fails.
             mkdir -p /tmp/statediff
             git clone https://github.com/filecoin-project/statediff.git /tmp/statediff
             cd /tmp/statediff
-            go generate ./...
-            go install ./cmd/statediff
+            go install ./cmd/statediff || exit 0
       - run:
           name: go test
           environment: