GitHub: only run cover on some itests, send completion

We only want to run the coverage on some select tests, since we don't
want to make tests with slow backends even slower.
And because we use "parallel: true" when uploading the coverage results,
those will only be assembled once we send "parallel-finished: true"
using the goveralls action.
So we do that with a new "finish" job.

.github/workflows/main.yml

@@ -242,12 +242,15 @@ jobs:
         include:
           - name: btcd
             args: backend=btcd
+            cover: true
           - name: bitcoind
             args: backend=bitcoind
+            cover: true
           - name: bitcoind-notxindex
             args: backend="bitcoind notxindex"
           - name: bitcoind-rpcpolling
             args: backend="bitcoind rpcpolling"
+            cover: true
           - name: bitcoind-etcd
             args: backend=bitcoind dbbackend=etcd
           - name: bitcoind-postgres
@@ -274,12 +277,14 @@ jobs:
         run: ./scripts/install_bitcoind.sh $BITCOIN_VERSION
 
       - name: run ${{ matrix.name }}
-        run: make itest-parallel ${{ matrix.args }} cover=true
+        run: make itest-parallel ${{ matrix.args }} ${{ matrix.cover == true && 'cover=1' || '' }}
 
       - name: convert coverage data
+        if: ${{ matrix.cover == true }}
         run: go tool covdata textfmt -i=itest/cover -o itest/coverage.txt
 
       - name: Send coverage
+        if: ${{ matrix.cover == true }}
         uses: shogo82148/actions-goveralls@v1
         with:
           path-to-profile: itest/coverage.txt
@@ -410,3 +415,13 @@ jobs:
 
       - name: release notes check
         run: scripts/check-release-notes.sh
+
+  # Notify about the completion of all coverage collecting jobs.
+  finish:
+    if: ${{ always() }}
+    needs: [unit-test, ubuntu-integration-test]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: shogo82148/actions-goveralls@v1
+        with:
+          parallel-finished: true