Update pipeline.yml

Author: wsmoses

.buildkite/pipeline.yml

@@ -32,6 +32,7 @@ steps:
           cuda: "*"
         env:
           REACTANT_TEST_GROUP: "{{matrix.group}}"
+          CUDA_VISIBLE_DEVICES: 0
         if: build.message !~ /\[skip tests\]/
         timeout_in_minutes: 120