Add linux-dev-yaml to buildbot_steps.yml

The `linux-dev-yaml` builder is being used to test out the switchover
of the steps.yml file from the saltfs repo to the servo repo.

etc/ci/buildbot_steps.yml

@@ -39,6 +39,18 @@ linux-dev:
   - bash ./etc/ci/manifest_changed.sh
   - bash ./etc/ci/check_no_unwrap.sh
 
+linux-dev-yaml:
+  - ./mach test-tidy --no-progress --all
+  - ./mach test-tidy --no-progress --self-test
+  - ./mach build --dev
+  - ./mach test-compiletest
+  - ./mach test-unit
+  - ./mach build-cef
+  - ./mach build-geckolib
+  - bash ./etc/ci/lockfile_changed.sh
+  - bash ./etc/ci/manifest_changed.sh
+  - bash ./etc/ci/check_no_unwrap.sh
+
 linux-rel:
   - ./mach build --release
   - ./mach test-wpt-failure