Change working directory for Docker build

An attempt to use learnings from here:

actions/runner#1009

.github/workflows/gcc-problems.yml

@@ -64,6 +64,10 @@ jobs:
     runs-on: ubuntu-latest
     needs: gen_build_container
     steps:
+      - 
+        # TODO: Is this is necessary for overlays into the Docker container below?
+        name: Check Out Repo 
+        uses: actions/checkout@v2
       -
         # I am using mmagician fork of get-changed-files (forked from jitterbit/get-changed-files)
         #   Rationale: our workflow (merge branch into upstream master) is incompatible
@@ -87,6 +91,10 @@ jobs:
         run: |
           docker load --input /tmp/mme_builder.tar
           docker image ls -a
+      -
+        # Trying to diagnose missing /github/ mounts in container
+        name: Capture docker logs
+        uses: jwalton/gh-docker-logs@v1
       -
         # If needed https://github.com/microsoft/vscode-cpptools/issues/2266 for path fixups
         #
@@ -99,8 +107,14 @@ jobs:
         uses: addnab/docker-run-action@v2
         with:
           image: magma/mme_builder:latest
-          # TODO: Break up this long line (can I use '\' at end of each line?)
-          run: cd /magma/lte/gateway;make build_oai 2>&1 > /compile.log;for file in ${{ steps.changed_files.outputs.all }}; do grep $file /compile.log | xo '/\/magma\/((.*):(\d+):(\d+):\s+(?:fatal\s)?(warning|error):\s+(.*))/$1/' || true; done;
+          run: |
+            echo "Github Workspace SHM: $GITHUB_WORKSPACE"
+            ls -R /github/
+            cd $GITHUB_WORKSPACE/lte/gateway/
+            make build_oai 2>&1 > /compile.log
+            for file in ${{ steps.changed_files.outputs.all }};
+            do grep $file /compile.log | xo '/\/magma\/((.*):(\d+):(\d+):\s+(?:fatal\s)?(warning|error):\s+(.*))/$1/' || true;
+            done;
       -
         name: Store oai_build_logs artifact
         uses: actions/upload-artifact@v2