Auto merge of #20135 - servo:jdm-patch-13, r=Manishearth

Clean up after some disk-space intensive builds.

This should help the ongoing disk usage problems.

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etc/ci/buildbot_steps.yml

@@ -116,6 +116,7 @@ linux-dev:
     - bash ./etc/ci/lockfile_changed.sh
     - bash ./etc/ci/manifest_changed.sh
     - bash ./etc/ci/check_no_panic.sh
+    - ./etc/ci/clean_build_artifacts.sh
 
 linux-rel-wpt:
   env:
@@ -146,6 +147,7 @@ linux-rel-css:
     - ./mach test-stylo --release
     - bash ./etc/ci/lockfile_changed.sh
     - bash ./etc/ci/manifest_changed.sh
+    - ./etc/ci/clean_build_artifacts.sh
 
 linux-nightly:
   - ./mach clean-nightlies --keep 3 --force