Add cygwin support (#106)

* Add cygwin support

* Add build.rs to make CI happy

* Use lints in Cargo.toml

* Add TODO to remove the lint config later

---------

Co-authored-by: Chris Wong <lambda.fairy@gmail.com>

Author: Berrysoft

CHANGELOG.md

@@ -3,6 +3,9 @@
 - Add VxWorks support
   [#105](https://github.com/lambda-fairy/rust-errno/pull/105)
 
+- Add cygwin support
+  [#106](https://github.com/lambda-fairy/rust-errno/pull/106)
+
 # [0.3.10] - 2024-11-29
 
 - Update to windows-sys 0.59

Cargo.toml

@@ -31,3 +31,9 @@ libc = { version = "0.2", default-features = false }
 [features]
 default = ["std"]
 std = ["libc/std"]
+
+# TODO: Remove this exemption when Cygwin support lands in Rust stable
+# https://github.com/rust-lang/rust/pull/134999
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = ['cfg(target_os, values("cygwin"))']

src/unix.rs

@@ -78,6 +78,7 @@ extern "C" {
             target_os = "android",
             target_os = "espidf",
             target_os = "vxworks",
+            target_os = "cygwin",
             target_env = "newlib"
         ),
         link_name = "__errno"