Add bors environment to CI

This will be used to access secrets once we move off rust-lang-ci.

Author: Kobzol

.github/workflows/ci.yml

@@ -73,6 +73,7 @@ jobs:
     needs: [ calculate_matrix ]
     runs-on: "${{ matrix.os }}"
     timeout-minutes: 360
+    environment: ${{ ((github.repository == 'rust-lang/rust' && (github.ref == 'refs/heads/try' || github.ref == 'refs/heads/auto')) && 'bors') || '' }}
     env:
       CI_JOB_NAME: ${{ matrix.name }}
       CI_JOB_DOC_URL: ${{ matrix.doc_url }}