Build and test in parallel in CI

Build and test in parallel with as many jobs as we have been allocated
CPU cores. This should make CI runs faster and provide visibility to
parallel build problems.

.github/workflows/main.yml

@@ -17,22 +17,28 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: install packages
+      id: info
       run: |
         case $RUNNER_OS in
           Linux)
             sudo apt-get install autoconf autoconf-archive automake flex libpcre2-dev libtool
+            cpus=$(nproc)
             ;;
           macOS)
             brew install autoconf autoconf-archive automake pcre2 libtool
+            cpus=$(sysctl -n hw.activecpu)
             ;;
+          *)
+            cpus=1
         esac
+        echo "cpus=$cpus" >> "$GITHUB_OUTPUT"
     - name: autogen
       run: ./autogen.sh --no-configure
     - name: configure
       run: ./configure --disable-silent-rules
     - name: make
-      run: make
+      run: make -j${{ steps.info.outputs.cpus }}
     - name: make check
-      run: make check
+      run: make check -j${{ steps.info.outputs.cpus }}
     - name: make distcheck
-      run: make distcheck
+      run: make distcheck -j${{ steps.info.outputs.cpus }}