Add missing apt-get update step. Add actionlint.yaml to allow custom runner label to pass linting

Author: dsroberts

.github/actionlint.yaml

@@ -0,0 +1,3 @@
+self-hosted-runner:
+  labels:
+    - gpu

.github/workflows/core.yml

@@ -495,6 +495,9 @@ jobs:
       PYTEST_MPI_MAX_NPROCS: 8
     steps:
       - name: Confirm Nvidia GPUs are enabled
+        # The presence of the nvidia-smi command indicates that the Nvidia drivers have
+        # successfully been imported inot the container, there is no point continuing
+        # if nvidia-smi is not present
         run: nvidia-smi
 
       - name: Fix HOME
@@ -503,14 +506,19 @@ jobs:
         # (https://github.com/actions/runner/issues/863)
         run: echo "HOME=/root" >> "$GITHUB_ENV"
 
-      - name: Pre-run cleanup
-        # Make sure the current directory is empty
-        run: find . -delete
 
       # Git is needed for actions/checkout and Python for firedrake-configure
       # curl needed for adding new deb repositories to ubuntu
       - name: Install system dependencies (1)
-        run: apt-get -y install git python3 curl
+        run: |
+          apt-get update
+          apt-get -y install git python3 curl
+
+
+      - name: Pre-run cleanup
+        # Make sure the current directory is empty
+        run: find . -delete
+
 
       - name: Add Nvidia CUDA deb repositories
         run: |

firedrake/preconditioners/offload.py

@@ -9,7 +9,6 @@
 __all__ = ("OffloadPC",)
 
 
-
 @cache
 def offload_mat_type(pc_comm_rank) -> str | None:
     mat_type = device_matrix_type()