Antithesis docker workflow (#2877)

## Issue Addressed

Automates a build and push to antithesis servers on merges to unstable. They run tests against lighthouse daily and have requested more frequent pushes. Currently we are just manually pushing stable images when we have a new release.

## Proposed Changes

- Add a `Dockerfile.libvoidstar`
- Add the `libvoidstar.so` binary
- Add a new workflow to autmatically build and push on merges to unstable

## Additional Info
Requires adding the following secrets
-`ANTITHESIS_USERNAME`
-`ANTITHESIS_PASSWORD`
-`ANTITHESIS_REPOSITORY`
-`ANTITHESIS_SERVER`

Tested here: https://github.com/realbigsean/lighthouse/actions/runs/1612821446

Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: realbigsean <sean@sigmaprime.io>

.github/workflows/docker-antithesis.yml

@@ -0,0 +1,31 @@
+name: docker antithesis
+
+on:
+    push:
+        branches:
+            - unstable
+
+env:
+    ANTITHESIS_PASSWORD: ${{ secrets.ANTITHESIS_PASSWORD }}
+    ANTITHESIS_USERNAME: ${{ secrets.ANTITHESIS_USERNAME }}
+    ANTITHESIS_SERVER: ${{ secrets.ANTITHESIS_SERVER }}
+    REPOSITORY: ${{ secrets.ANTITHESIS_REPOSITORY }}
+    IMAGE_NAME: lighthouse
+    TAG: libvoidstar
+
+jobs:
+    build-docker:
+        runs-on: ubuntu-18.04
+        steps:
+            - uses: actions/checkout@v2
+            - name: Update Rust
+              run: rustup update stable
+            - name: Dockerhub login
+              run: |
+                  echo "${ANTITHESIS_PASSWORD}" | docker login --username ${ANTITHESIS_USERNAME} https://${ANTITHESIS_SERVER} --password-stdin
+            - name: Build AMD64 dockerfile (with push)
+              run: |
+                  docker build \
+                      --tag ${ANTITHESIS_SERVER}/${REPOSITORY}/${IMAGE_NAME}:${TAG} \
+                      --file ./testing/antithesis/Dockerfile.libvoidstar .
+                  docker push ${ANTITHESIS_SERVER}/${REPOSITORY}/${IMAGE_NAME}:${TAG}