[Singularity] Add documentation

.github/workflows/singularity-quicktest.yml

@@ -8,9 +8,10 @@ on:
 
 jobs:
   build_and_test:
+    name: Build and test Singularity container
     runs-on: ubuntu-22.04
     steps:
-      - name: checkout
+      - name: Checkout
         uses: actions/checkout@v3
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v2
@@ -26,6 +27,7 @@ jobs:
         with:
           file: docker/Dockerfile.finn
           context: .
+          load: true
           tags: finn_docker_export:latest
       - name: Build Singularity image
         run: singularity build finn_singularity_image.sif docker-daemon://finn_docker_export:latest

docs/finn/getting_started.rst

@@ -116,6 +116,7 @@ These are summarized below:
 * (optional) ``FINN_SKIP_DEP_REPOS`` (default "0") skips the download of FINN dependency repos (uses the ones already downloaded under deps/.
 * (optional) ``NVIDIA_VISIBLE_DEVICES`` (default "") specifies specific Nvidia GPUs to use in Docker container. Possible values are a comma-separated list of GPU UUID(s) or index(es) e.g. ``0,1,2``, ``all``, ``none``, or void/empty/unset.
 * (optional) ``DOCKER_BUILDKIT`` (default "1") enables `Docker BuildKit <https://docs.docker.com/develop/develop-images/build_enhancements/>`_ for faster Docker image rebuilding (recommended).
+* (optional) ``FINN_SINGULARITY`` (default "") points to a pre-built Singularity image to use instead of the Docker image. Singularity support is experimental and intended only for systems where Docker is unavailable. Does not support GPUs.
 
 General FINN Docker tips
 ************************