CI: Add NetBSD target (#180)

* Remove the `sys-info` crate

It offers much more features than we currently use.

Additionally, it was preventing me to cross-compile for NetBSD.

Since we were just using the `hostname()` function from the crate,
I went ahead and stole it.

* Add NetBSD target

* Fix FreeBSD clippy warnings

.github/workflows/check-and-lint.yaml

@@ -56,6 +56,11 @@ jobs:
             target_name: macOS
             os: macos-11
 
+          - target: x86_64-unknown-netbsd
+            target_name: NetBSD
+            use_cross: true
+            os: ubuntu-20.04
+
           - target: x86_64-pc-windows-msvc
             target_name: Windows
             os: windows-2019