CI: Run bitrot build jobs in parallel

These were previously run serially in the same job to take advantage of
caching from earlier build files. However, after the main build was
split into a separate job, `actions/cache` is primed by it, so all of
the bitrot tests are going to start with caches and don't need to rely
on cross-build-flag caching.

.github/workflows/ci.yml

@@ -57,6 +57,7 @@ jobs:
 
     outputs:
       build_matrix: ${{ steps.set-matrices.outputs.build_matrix }}
+      build_names: ${{ steps.set-matrices.outputs.build_names }}
       test_matrix: ${{ steps.set-matrices.outputs.test_matrix }}
       test_names: ${{ steps.set-matrices.outputs.test_names }}
     steps:
@@ -65,6 +66,7 @@ jobs:
           CFG: ${{ toJSON(matrix.cfg) }}
         run: |
           jq -r -n 'env.CFG | fromjson | @json "build_matrix=\(.data)"' >> $GITHUB_OUTPUT
+          jq -r -n 'env.CFG | fromjson | [.data[] | .name] | @json "build_names=\(.)"' >> $GITHUB_OUTPUT
           jq -r -n 'env.CFG | fromjson | [.data[] | select(.test_os)] | @json "test_matrix=\(.)"' >> $GITHUB_OUTPUT
           jq -r -n 'env.CFG | fromjson | [.data[] | select(.test_os) | .name] | @json "test_names=\(.)"' >> $GITHUB_OUTPUT
 
@@ -150,12 +152,17 @@ jobs:
           path: ${{ format('src/zcash-gtest{0}', matrix.file_ext) }}
 
   bitrot:
-    name: Bitrot check tier ${{ matrix.tier }} platform ${{ matrix.platform }}
+    name: Bitrot check tier ${{ matrix.tier }} platform ${{ matrix.platform }} flag '${{ matrix.configure_flag }}'
     needs: [matrices, build]
     runs-on: ${{ matrix.build_os }}
     continue-on-error: ${{ matrix.tier == 3 }}
     strategy:
       matrix:
+        name: ${{ fromJson(needs.matrices.outputs.build_names) }}
+        configure_flag:
+          - '--with-libs'
+          - '--disable-wallet'
+          - '--disable-mining'
         include: ${{ fromJson(needs.matrices.outputs.build_matrix) }}
 
     steps:
@@ -201,23 +208,9 @@ jobs:
         shell: bash
         run: echo "count=$(nproc 2> /dev/null || sysctl -n hw.logicalcpu)" >> "$GITHUB_OUTPUT"
 
-      - name: Build zcashd with libraries enabled
+      - name: Build zcashd with the flag being checked
         run: >
-          CONFIGURE_FLAGS="--with-libs"
-          ${{ matrix.host }}
-          ./zcutil/build.sh
-          -j"${{ steps.nproc.outputs.count }}"
-
-      - name: Build zcashd with wallet disabled
-        run: >
-          CONFIGURE_FLAGS="--disable-wallet"
-          ${{ matrix.host }}
-          ./zcutil/build.sh
-          -j"${{ steps.nproc.outputs.count }}"
-
-      - name: Build zcashd with mining disabled
-        run: >
-          CONFIGURE_FLAGS="--disable-mining"
+          CONFIGURE_FLAGS="${{ matrix.configure_flag }}"
           ${{ matrix.host }}
           ./zcutil/build.sh
           -j"${{ steps.nproc.outputs.count }}"