GHA MacOS Only Sign/Notarize if self repo

.github/workflows/desktop-build.yml

@@ -270,6 +270,8 @@ jobs:
         # https://docs.github.com/en/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories
         # https://github.com/actions/runner-images?tab=readme-ov-file#available-images
         run: |
+          if [[ -n "$MACOS_CERTIFICATE_NAME" ]]
+          then
             echo $MACOS_CERTIFICATE | base64 --decode > certificate.p12
             security create-keychain -p "$MACOS_CI_KEYCHAIN_PWD" build.keychain
             security default-keychain -s build.keychain
@@ -277,6 +279,7 @@ jobs:
             security unlock-keychain -p "$MACOS_CI_KEYCHAIN_PWD" build.keychain
             security import certificate.p12 -k build.keychain -P "$MACOS_CERTIFICATE_PWD" -T /usr/bin/codesign
             security set-key-partition-list -S apple-tool:,apple:,codesign: -s -k "$MACOS_CI_KEYCHAIN_PWD" build.keychain
+          fi
           .ci/compile.sh --server --parallel ${{matrix.core_count}}
 
       - name: Sign app bundle
@@ -285,8 +288,11 @@ jobs:
           MACOS_CERTIFICATE_NAME: ${{ secrets.PROD_MACOS_CERTIFICATE_NAME }}
           MACOS_CI_KEYCHAIN_PWD: ${{ secrets.PROD_MACOS_CI_KEYCHAIN_PWD }}
         run: |
+          if [[ -n "$MACOS_CERTIFICATE_NAME" ]]
+          then
             security unlock-keychain -p "$MACOS_CI_KEYCHAIN_PWD" build.keychain
             /usr/bin/codesign --sign="$MACOS_CERTIFICATE_NAME" --entitlements=".ci/macos.entitlements" --options=runtime --force --deep --timestamp --verbose ${{steps.build.outputs.path}}
+          fi
 
       - name: Notarize app bundle
         if: matrix.make_package
@@ -295,6 +301,8 @@ jobs:
           MACOS_NOTARIZATION_TEAM_ID: ${{ secrets.PROD_MACOS_NOTARIZATION_TEAM_ID }}
           MACOS_NOTARIZATION_PWD: ${{ secrets.PROD_MACOS_NOTARIZATION_PWD }}
         run: |
+          if [[ -n "$MACOS_NOTARIZATION_APPLE_ID" ]]
+          then
             # Store the notarization credentials so that we can prevent a UI password dialog from blocking the CI
             echo "Create keychain profile"
             xcrun notarytool store-credentials "notarytool-profile" --apple-id "$MACOS_NOTARIZATION_APPLE_ID" --team-id "$MACOS_NOTARIZATION_TEAM_ID" --password "$MACOS_NOTARIZATION_PWD"
@@ -316,6 +324,7 @@ jobs:
             # validated by macOS even when an internet connection is not available.
             echo "Attach staple"
             xcrun stapler staple ${{steps.build.outputs.path}}
+          fi
 
       - name: Upload artifact
         if: matrix.make_package