ci: gate cuda san on cuda changes (#8438)

CUDA san is slow gate it on CUDA changes. This is will post commit with
san

---------

Signed-off-by: Joe Isaacs <joe.isaacs@live.co.uk>

Author: joseph-isaacs

.github/workflows/cuda.yaml

@@ -21,6 +21,26 @@ env:
   RUST_BACKTRACE: 1
 
 jobs:
+  changes:
+    name: "Detect CUDA changes"
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      pull-requests: read
+    outputs:
+      run-cuda-san: ${{ github.event_name != 'pull_request' || steps.filter.outputs.cuda == 'true' }}
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10  # v6
+      - uses: dorny/paths-filter@fbd0ab8f3e69293af611ebaee6363fc25e6d187d  # v4
+        id: filter
+        if: github.event_name == 'pull_request'
+        with:
+          filters: |
+            cuda:
+              - "vortex-cuda/**"
+              - "vortex-test/**"
+              - ".github/workflows/**"
+
   cuda-build-lint:
     if: github.repository == 'vortex-data/vortex'
     name: "CUDA build & lint"
@@ -92,7 +112,10 @@ jobs:
             --verbose
 
   cuda-test-sanitizer:
-    if: github.repository == 'vortex-data/vortex'
+    needs: [changes]
+    if: >-
+      always() && github.repository == 'vortex-data/vortex' &&
+      needs.changes.outputs.run-cuda-san == 'true'
     name: "CUDA tests (${{ matrix.sanitizer }})"
     timeout-minutes: 30
     runs-on: runs-on=${{ github.run_id }}/runner=gpu/tag=cuda-test-sanitizer