Add CI stage for memory benchmark (#981)

This PR adds the CI stage for #976, which compares `main`'s result to
the feature branch's result. This CI will not pass until #976 goes in.

Eventually, we should probably write our own Github Action to combine
the benchmarks from #955 and these memory benchmarks into one PR
comment. That'll reduce the noisy github-actions bot comments.

.github/workflows/ci.yml

@@ -148,3 +148,41 @@ jobs:
           branchName: ${{ github.base_ref }}
           cwd: "compiler/qsc"
         if: ${{ github.base_ref != null }}
+  runMemoryProfile:
+    name: run memory profile
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          ref: main
+      - uses: Swatinem/rust-cache@v2
+      - run: |
+          MAIN_MEASUREMENT=$(cargo run --bin memtest)
+          echo "MAIN_MEASUREMENT<<EOF" >> $GITHUB_ENV
+          echo "$MAIN_MEASUREMENT" >> $GITHUB_ENV
+          echo "EOF" >> $GITHUB_ENV
+      - run: |
+          echo "${{env.MAIN_MEASUREMENT}}"
+          echo $MAIN_MEASUREMENT
+
+      - uses: actions/checkout@v2
+      - run: |
+          BRANCH_MEASUREMENT=$(cargo run --bin memtest)
+          echo "BRANCH_MEASUREMENT<<EOF" >> $GITHUB_ENV
+          echo "$BRANCH_MEASUREMENT" >> $GITHUB_ENV
+          echo "EOF" >> $GITHUB_ENV
+      - run: |
+          echo "${{env.BRANCH_MEASUREMENT}}"
+          echo $BRANCH_MEASUREMENT
+      - uses: actions/github-script@v6
+        with:
+          script: |
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: `## Memory Report for ${{ github.sha }}
+            | Test                        | This Branch | On Main  |
+            |-----------------------------|-------------|----------|
+            | compile core + standard lib | ${{ env.BRANCH_MEASUREMENT }} bytes | ${{ env.MAIN_MEASUREMENT }} bytes |`
+            })