build: configure S3 cache once

Author: jmgilman

.github/workflows/nix.yml

@@ -28,6 +28,7 @@ concurrency:
 
 env:
   ECR_REGISTRY: 432820653916.dkr.ecr.eu-central-1.amazonaws.com
+  S3_CACHE: s3://iog-catalyst-nix-cache?region=eu-central-1
 
 jobs:
   discover:
@@ -65,7 +66,7 @@ jobs:
           nix_key: ${{ secrets.NIX_SIGNING_KEY }}
           s3_id: ${{ secrets.AWS_ACCESS_KEY_ID }}
           s3_key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-          cache: s3://iog-catalyst-nix-cache?region=eu-central-1
+          cache: ${{ env.S3_CACHE }}
   build-packages:
     if: always()
     needs:
@@ -86,7 +87,7 @@ jobs:
           nix_key: ${{ secrets.NIX_SIGNING_KEY }}
           s3_id: ${{ secrets.AWS_ACCESS_KEY_ID }}
           s3_key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-          cache: s3://iog-catalyst-nix-cache?region=eu-central-1
+          cache: ${{ env.S3_CACHE }}
   build-devshells:
     if: always()
     needs:
@@ -107,4 +108,4 @@ jobs:
           nix_key: ${{ secrets.NIX_SIGNING_KEY }}
           s3_id: ${{ secrets.AWS_ACCESS_KEY_ID }}
           s3_key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-          cache: s3://iog-catalyst-nix-cache?region=eu-central-1
+          cache: ${{ env.S3_CACHE }}