Serialize workflows using Nix caching

Alleviates the pressure on the GitHub action cache by only allowing a
single nix-caching job at a time.

Fixes TraceMachina#464
Fixes TraceMachina#611

.github/workflows/image.yaml

@@ -12,7 +12,7 @@ permissions: read-all
 
 jobs:
   publish-image:
-    runs-on: large-ubuntu-22.04
+    runs-on: ubuntu-22.04
     permissions:
       packages: write
       id-token: write
@@ -28,9 +28,9 @@ jobs:
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
 
-      # - name: Cache Nix derivations TODO(aaronmondal): revisit this bit when there are less flakes or it is more understood
-        # uses: >- # Custom commit, last pinned at 2023-11-17.
-          # DeterminateSystems/magic-nix-cache-action@a04e6275a6bea232cd04fc6f3cbf20d4cb02a3e1
+      - name: Cache Nix derivations
+        uses: >- # Custom commit, last pinned at 2023-11-17.
+          DeterminateSystems/magic-nix-cache-action@a04e6275a6bea232cd04fc6f3cbf20d4cb02a3e1
 
       - name: Test image
         run: |

.github/workflows/lre.yaml

@@ -2,10 +2,10 @@
 name: Local Remote Execution
 
 on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
+  workflow_run:
+    workflows: ["Create OCI image"]
+    types:
+      - completed
 
 permissions: read-all
 
@@ -43,7 +43,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [large-ubuntu-22.04]
+        os: [ubuntu-22.04]
     name: Remote / ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     steps: