Add cirrus CI

.cirrus.yml

@@ -0,0 +1,28 @@
+test_task:
+  matrix:
+    - container:
+        image: rust:latest
+    - allow_failures: true
+      container:
+        image: rustlang/rust:nightly
+  cargo_cache:
+    folder: $CARGO_HOME/registry
+    fingerprint_script: cat Cargo.lock
+  build_script: cargo build
+  test_script: cargo test
+  before_cache_script: rm -rf $CARGO_HOME/registry/index
+
+freebsd_instance:
+  image-family: freebsd-13-0
+
+task:
+  name: cargo test (stable)
+  env:
+    HOME: /tmp # cargo needs it
+  install_script: pkg install -y rust
+  cargo_cache:
+    folder: $HOME/.cargo/registry
+    fingerprint_script: cat Cargo.lock
+  build_script: cargo build --all
+  test_script: cargo test --all --all-targets
+  before_cache_script: rm -rf $HOME/.cargo/registry/index