coverity-scan.yml: use get-etag.sh

+ fail if not able to fetch (same as in ccpp.yml)

Author: MartinPulec

.github/workflows/coverity-scan.yml

@@ -46,7 +46,9 @@ jobs:
       if: ${{ env.coverity_token }}
       id: etags
       run: |
-        echo "ndi=$($GITHUB_WORKSPACE/.github/scripts/get-etags.sh https://downloads.ndi.tv/SDK/NDI_SDK_Linux/Install_NDI_SDK_v6_Linux.tar.gz)" >> $GITHUB_OUTPUT
+        { printf ndi=; $GITHUB_WORKSPACE/.github/scripts/get-etag.sh\
+         https://downloads.ndi.tv/SDK/NDI_SDK_Linux/Install_NDI_SDK_v6_Linux.\
+        tar.gz; } >> $GITHUB_OUTPUT
     - name: Run actions/cache for NDI
       if: ${{ env.coverity_token }}
       id: cache-ndi