Benchmark project builds and output sizes in CI (#9272)

The benchmarks only replayed single bsc calls, so the build system's own
work never showed. They now also build the base's tests/tests on one worker
domain (clean, no-op, leaf edit, shared edit), adding the workers'
allocations the build reports, and measure the .cmi/.cmti/.cmt/.cmj sizes
and the playground bundle. Only the no-op and leaf-edit builds run under
cachegrind: the larger ones take minutes, and with two domains collecting
their instructions depend on how the domains interleave.

Review: Why build the base's tests/tests on both sides? The base compiler
builds them already, so a pull request adding tests with new syntax can't
break the base measurement.


Claude-Session: https://claude.ai/code/session_01Kbf3gGPsF3fHZn9rBxA7Hm

Signed-off-by: Christoph Knittel <ck@cca.io>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: cknitt

.github/workflows/ci.yml

@@ -428,6 +428,12 @@ jobs:
           git worktree add --detach "$RUNNER_TEMP/base" HEAD^1
           opam exec -- dune build --root "$RUNNER_TEMP/base" --display quiet
 
+      # For the size of the bundle only; the playground is tested elsewhere.
+      - name: Build the playground compilers
+        run: |
+          opam exec -- make playground-compiler
+          opam exec -- make -C "$RUNNER_TEMP/base" playground-compiler
+
       - name: Measure and compare
         env:
           RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
@@ -437,12 +443,14 @@ jobs:
           # little, and the instructions of the runtime and Belt files by up
           # to 0.2%. The runtime and Belt are built there too, since the
           # replayed builds would otherwise write interfaces that don't
-          # match those of the files they don't replay yet.
+          # match those of the files they don't replay yet. Both build the
+          # base's tests/tests, which the base's compiler builds already.
           measure() {
             sudo mkdir -p /bench
             sudo mount --bind "$1" /bench
             node scripts/compilerBenchmarks.js prepare /bench
-            node scripts/compilerBenchmarks.js measure /bench "$2" --instructions
+            node scripts/compilerBenchmarks.js measure /bench "$2" --instructions \
+              --project "$RUNNER_TEMP/base" --playground
             sudo umount /bench
           }
           measure "$RUNNER_TEMP/base" "$RUNNER_TEMP/base.json"