Add support in objc2 for running GNUStep on Apple systems

And in the future ObjFW

Author: madsmtm

objc2/Cargo.toml

@@ -21,6 +21,8 @@ exclude = [
     "tests-ios/**",
 ]
 
+build = "build.rs"
+
 [features]
 exception = ["objc2_exception"]
 verify_message = []

objc2/build.rs

@@ -0,0 +1,9 @@
+use std::env;
+
+fn main() {
+    // The script doesn't depend on our code
+    println!("cargo:rerun-if-changed=build.rs");
+
+    let runtime = env::var("DEP_OBJC_RUNTIME").unwrap();
+    println!("cargo:rustc-cfg={}", runtime);
+}

objc2/src/lib.rs

@@ -106,7 +106,7 @@ mod test_utils;
 ///
 /// This is a temporary solution to make our CI work for now!
 #[doc(hidden)]
-#[cfg(not(target_vendor = "apple"))]
+#[cfg(any(gnustep, winobjc))]
 pub mod __gnustep_hack {
     use super::runtime::Class;
 

objc2/src/message/mod.rs

@@ -28,10 +28,10 @@ unsafe fn conditional_try<R: Encode>(f: impl FnOnce() -> R) -> Result<R, Message
 
 mod verify;
 
-#[cfg(target_vendor = "apple")]
+#[cfg(apple)]
 #[path = "apple/mod.rs"]
 mod platform;
-#[cfg(not(target_vendor = "apple"))]
+#[cfg(any(gnustep, winobjc))]
 #[path = "gnustep.rs"]
 mod platform;
 

objc2/tests/use_macros.rs

@@ -1,4 +1,4 @@
-#![cfg(target_vendor = "apple")]
+#![cfg(target_vendor = "apple")] // Temporary
 
 use objc2::runtime::Object;
 use objc2::{class, msg_send, sel};