Auto merge of #29538 - mrobinson:run-layout-2020-build-in-main-workflow, r=jdm

Run the Layout 2020 build in the main workflow

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because they are an infrastructure change.

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.github/workflows/main.yml

@@ -184,6 +184,8 @@ jobs:
         with:
           name: release-binary
           path: target.tar.gz
+      - name: Release build (Layout 2020)
+        run: python3 ./mach build --release --with-layout-2020
 
   linux-wpt:
     if: contains(fromJSON('["auto", "try", "try-wpt"]'), github.ref_name)