Add tmate

Author: mhsmith

.github/workflows/build.yml

@@ -350,6 +350,7 @@ jobs:
 
     runs-on: ${{ matrix.runs-on }}
     steps:
+      - uses: mxschmitt/action-tmate@v3  # FIXME
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           persist-credentials: false