[antlir][oss] github actions ci

.github/workflows/tests.yml

@@ -0,0 +1,20 @@
+name: Tests
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: true
+      - uses: facebook/install-dotslash@latest
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: nightly
+      - name: Validate targets
+        run: |
+          ./buck2 audit providers --quiet //...
+      - name: Build layer with RPMs
+        run: |
+          ./buck2 build antlir//antlir/antlir2/features/rpm/tests:simple--layer