ci: Install missing nproc in macos task

This avoids special-casing macos

.github/workflows/ci.yml

@@ -105,7 +105,7 @@ jobs:
         run: |
           # A workaround for "The `brew link` step did not complete successfully" error.
           brew install --quiet python@3 || brew link --overwrite python@3
-          brew install --quiet ninja pkg-config gnu-getopt ccache boost libevent miniupnpc zeromq qt@5 qrencode
+          brew install --quiet coreutils ninja pkg-config gnu-getopt ccache boost libevent miniupnpc zeromq qt@5 qrencode
 
       - name: Set Ccache directory
         run: echo "CCACHE_DIR=${RUNNER_TEMP}/ccache_dir" >> "$GITHUB_ENV"