CI: use self-hosted runners for Linux build jobs (#33321)

* CI: use self-hosted runners for Linux build jobs

Signed-off-by: Delan Azabani <dazabani@igalia.com>

* Set ccache and incremental env variables when not self-hosted

Signed-off-by: Delan Azabani <dazabani@igalia.com>

* Force GitHub-hosted runner when in upload mode

Signed-off-by: Delan Azabani <dazabani@igalia.com>

* Revert s/python/python3/ now that our image has python

Signed-off-by: Delan Azabani <dazabani@igalia.com>

* Remove stray comment in timeout workflow

Signed-off-by: Delan Azabani <dazabani@igalia.com>

* Update description of runner-select job

Signed-off-by: Delan Azabani <dazabani@igalia.com>

* Apply suggestions from code review

Address couple minor naming / formatting nits

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

---------

Signed-off-by: Delan Azabani <dazabani@igalia.com>
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

.github/workflows/linux.yml

@@ -59,43 +59,89 @@ on:
 env:
   RUST_BACKTRACE: 1
   SHELL: /bin/bash
-  SCCACHE_GHA_ENABLED: "true"
-  RUSTC_WRAPPER: "sccache"
-  CCACHE: "sccache"
-  CARGO_INCREMENTAL: 0
 
 jobs:
+  # Runs the underlying job (“workload”) on a self-hosted runner if available,
+  # with the help of a `runner-select` job and a `runner-timeout` job.
+  runner-select:
+    uses: ./.github/workflows/self-hosted-runner-select.yml
+    secrets: inherit
+    with:
+      # Ubuntu 22.04 has glibc 2.34 so the binaries produced
+      # won't run on systems with older glibc e.g wpt.fyi
+      # runners which still use 20.04.
+      github-hosted-runner-label: ubuntu-${{ inputs.upload && '20.04' || '22.04' }}
+      self-hosted-image-name: servo-ubuntu2204
+      force-github-hosted-runner: ${{ inputs.upload }}
+  runner-timeout:
+    needs:
+      - runner-select
+    uses: ./.github/workflows/self-hosted-runner-timeout.yml
+    secrets: inherit
+    with:
+      selected-runner-label: ${{ needs.runner-select.outputs.selected-runner-label }}
+      is-self-hosted: ${{ fromJSON(needs.runner-select.outputs.is-self-hosted) }}
+
   build:
-    name: Linux Build
-    # Ubuntu 22.04 has glibc 2.34 so the binaries produced
-    # won't run on systems with older glibc e.g wpt.fyi
-    # runners which still use 20.04.
-    runs-on: ubuntu-${{ inputs.upload && '20.04' || '22.04' }}
+    needs:
+      - runner-select
+    name: Linux Build [${{ needs.runner-select.outputs.unique-id }}]
+    runs-on: ${{ needs.runner-select.outputs.selected-runner-label }}
     steps:
+      - if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) }}
+        run: |
+          echo SCCACHE_GHA_ENABLED=true >> $GITHUB_ENV
+          echo RUSTC_WRAPPER=sccache >> $GITHUB_ENV
+          echo CCACHE=sccache >> $GITHUB_ENV
+          echo CARGO_INCREMENTAL=0 >> $GITHUB_ENV
+
       - uses: actions/checkout@v4
-        if: github.event_name != 'pull_request_target'
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) && github.event_name != 'pull_request_target' }}
       # This is necessary to checkout the pull request if this run was triggered via a
       # `pull_request_target` event.
       - uses: actions/checkout@v4
-        if: github.event_name == 'pull_request_target'
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) && github.event_name == 'pull_request_target' }}
         with:
           ref: ${{ github.event.pull_request.head.sha }}
+
+      # Faster checkout for self-hosted runner that uses prebaked repo.
+      - if: ${{ fromJSON(needs.runner-select.outputs.is-self-hosted) && github.event_name != 'pull_request_target' }}
+        run: git fetch --depth=1 origin $env:GITHUB_SHA
+      - if: ${{ fromJSON(needs.runner-select.outputs.is-self-hosted) && github.event_name == 'pull_request_target' }}
+        run: git fetch --depth=1 origin refs/pull/${{ github.event_number }}/head
+      - if: ${{ fromJSON(needs.runner-select.outputs.is-self-hosted) }}
+        # Same as `git switch --detach FETCH_HEAD`, but fixes up dirty working
+        # trees, in case the runner image was baked with a dirty working tree.
+        run: |
+          git switch --detach
+          git reset --hard FETCH_HEAD
+
+      # Install missing tools in a GitHub-hosted runner.
       - name: Run sccache-cache
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) }}
         uses: mozilla-actions/sccache-action@v0.0.4
       - name: Set LIBCLANG_PATH env # needed for bindgen in mozangle
-        if: ${{ !inputs.upload  }} # not needed on ubuntu 20.04 used for nightly
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) && !inputs.upload }} # not needed on ubuntu 20.04 used for nightly
         run: echo "LIBCLANG_PATH=/usr/lib/llvm-14/lib" >> $GITHUB_ENV
       - uses: actions/setup-python@v5
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) }}
         with:
           python-version: '3.10'
-      - name: Install crown
-        run: cargo install --path support/crown
       - name: Bootstrap Python
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) }}
         run: python3 -m pip install --upgrade pip
       - name: Bootstrap dependencies
+        if: ${{ ! fromJSON(needs.runner-select.outputs.is-self-hosted) }}
         run: |
           sudo apt update
           python3 ./mach bootstrap --skip-lints
+
+      # Always install crown, even on self-hosted runners, because it is tightly
+      # coupled to the rustc version, and we may have the wrong version if the
+      # commit we are building uses a different rustc version.
+      - name: Install crown
+        run: cargo install --path support/crown
+
       - name: Build (${{ inputs.profile }})
         run: |
           python3 ./mach build --use-crown --locked --${{ inputs.profile }}