container repository name must be lowercase

.github/workflows/installer-library.yml

@@ -36,6 +36,12 @@ jobs:
     name: Prepare Docker Image Version Data
     runs-on: ubuntu-20.04
     steps:
+      -
+        name: Set gchr repository name
+        id: set-ghrc-repository
+        run: |
+          ghcr_name=$(echo "${GITHUB_REPOSITORY}" | awk '{ print tolower($0) }')
+          echo ::set-output name=repository::${ghcr_name}
       -
         name: Checkout
         uses: actions/checkout@v3
@@ -83,6 +89,8 @@ jobs:
 
     outputs:
 
+      ghcr-repository: ${{ steps.set-ghrc-repository.outputs.repository }}
+
       qpdf-json: ${{ steps.qpdf-setup.outputs.qpdf-json }}
 
       pikepdf-json: ${{ steps.pikepdf-setup.outputs.pikepdf-json }}
@@ -134,6 +142,6 @@ jobs:
       dockerfile: ./docker-builders/Dockerfile.pikepdf
       build-json: ${{ needs.prepare-docker-build.outputs.pikepdf-json }}
       build-args: |
-        REPO=${{ github.repository }}
+        REPO=${{ needs.prepare-docker-build.outputs.ghcr-repository }}
         QPDF_VERSION=${{ fromJSON(needs.prepare-docker-build.outputs.qpdf-json).version }}
         PIKEPDF_VERSION=${{ fromJSON(needs.prepare-docker-build.outputs.pikepdf-json).version }}