workflows: run smaller jobs on ubuntu-slim

This is in public preview now. These runners run in a docker container
with only a single vCPU instead of 4 like the other jobs. For most of
our jobs, this should be plenty, except for eval and linting.

.github/workflows/backport.yml

@@ -22,7 +22,7 @@ jobs:
   backport:
     name: Backport Pull Request
     if: vars.NIXPKGS_CI_APP_ID && github.event.pull_request.merged == true && (github.event.action != 'labeled' || startsWith(github.event.label.name, 'backport'))
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     timeout-minutes: 3
     steps:
       # Use a GitHub App to create the PR so that CI gets triggered

.github/workflows/bot.yml

@@ -39,7 +39,7 @@ defaults:
 
 jobs:
   run:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     if: github.event_name != 'schedule' || github.repository_owner == 'NixOS'
     env:
       # TODO: Remove after 2026-03-04, when Node 24 becomes the default.

.github/workflows/check.yml

@@ -32,7 +32,7 @@ jobs:
     if: inputs.baseBranch && inputs.headBranch
     permissions:
       pull-requests: write
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     timeout-minutes: 3
     steps:
       - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0

.github/workflows/comment.yml

@@ -19,7 +19,7 @@ jobs:
   # a reaction to these comments.
   react:
     name: React with eyes
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     timeout-minutes: 2
     if: contains(github.event.comment.body, '@NixOS/nixpkgs-merge-bot merge')
     steps:

.github/workflows/edited.yml

@@ -29,7 +29,7 @@ defaults:
 jobs:
   base:
     name: Trigger jobs
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-slim
     if: github.event.changes.base.ref.from && github.event.changes.base.ref.from != github.event.pull_request.base.ref
     timeout-minutes: 2
     steps:

.github/workflows/eval.yml

@@ -33,7 +33,7 @@ defaults:
 jobs:
   versions:
     if: inputs.testVersions
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     outputs:
       versions: ${{ steps.versions.outputs.versions }}
     steps:
@@ -257,7 +257,7 @@ jobs:
 
   # Creates a matrix of Eval performance for various versions and systems.
   report:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     needs: [versions, eval]
     steps:
       - name: Download output paths and eval stats for all versions

.github/workflows/merge-group.yml

@@ -18,7 +18,7 @@ permissions: {}
 
 jobs:
   prepare:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     outputs:
       baseBranch: ${{ steps.prepare.outputs.base }}
       mergedSha: ${{ steps.prepare.outputs.mergedSha }}
@@ -113,7 +113,7 @@ jobs:
     needs:
       - lint
       - eval
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     permissions:
       statuses: write
     steps:

.github/workflows/periodic-merge.yml

@@ -21,7 +21,7 @@ defaults:
 
 jobs:
   merge:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     timeout-minutes: 5
     steps:
       # Use a GitHub App to create the PR so that CI gets triggered

.github/workflows/pull-request-target.yml

@@ -19,7 +19,7 @@ permissions: {}
 
 jobs:
   prepare:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     permissions:
       # wrong branch review comment
       pull-requests: write
@@ -121,7 +121,7 @@ jobs:
       - lint
       - eval
       - build
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     permissions:
       statuses: write
     steps:

.github/workflows/review.yml

@@ -17,7 +17,7 @@ defaults:
 
 jobs:
   process:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     timeout-minutes: 2
     steps:
       - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0

.github/workflows/reviewed.yml

@@ -12,6 +12,6 @@ defaults:
 
 jobs:
   trigger:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     steps:
       - run: echo This is a no-op only used as a trigger for workflow_run.

.github/workflows/teams.yml

@@ -15,7 +15,7 @@ defaults:
 jobs:
   sync:
     if: github.event_name != 'schedule' || github.repository_owner == 'NixOS'
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     steps:
       # Use a GitHub App to create the PR so that CI gets triggered and to
       # request team member lists.

.github/workflows/test.yml

@@ -11,7 +11,7 @@ permissions: {}
 
 jobs:
   prepare:
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     outputs:
       merge-group: ${{ steps.files.outputs.merge-group }}
       mergedSha: ${{ steps.prepare.outputs.mergedSha }}