Add /System/iOSSupport to header/library search paths on Mac Catalyst (#961)

Author: madsmtm

src/lib.rs

@@ -2582,16 +2582,44 @@ impl Build {
  "Detecting {:?} SDK path for {}",
  os, sdk_details.sdk
  ));
- let sdk_path = if let Some(sdkroot) = env::var_os("SDKROOT") {
- sdkroot
- } else {
- self.apple_sdk_root(&sdk_details.sdk)?
- };
+ let sdk_path = self.apple_sdk_root(&sdk_details.sdk)?;
 
  cmd.args.push("-isysroot".into());
  cmd.args.push(sdk_path);
  }
 
+ if let AppleArchSpec::Catalyst(_) = arch {
+ // Mac Catalyst uses the macOS SDK, but to compile against and
+ // link to iOS-specific frameworks, we should have the support
+ // library stubs in the include and library search path.
+ let sdk_path = self.apple_sdk_root(&sdk_details.sdk)?;
+ let ios_support = PathBuf::from(sdk_path).join("/System/iOSSupport");
+
+ cmd.args.extend([
+ // Header search path
+ OsString::from("-isystem"),
+ ios_support.join("/usr/include").into(),
+ // Framework header search path
+ OsString::from("-iframework"),
+ ios_support.join("/System/Library/Frameworks").into(),
+ // Library search path
+ {
+ let mut s = OsString::from("-L");
+ s.push(&ios_support.join("/usr/lib"));
+ s
+ },
+ // Framework linker search path
+ {
+ // Technically, we _could_ avoid emitting `-F`, as
+ // `-iframework` implies it, but let's keep it in for
+ // clarity.
+ let mut s = OsString::from("-F");
+ s.push(&ios_support.join("/System/Library/Frameworks"));
+ s
+ },
+ ]);
+ }
+
  Ok(())
  }
 
@@ -3489,6 +3517,10 @@ impl Build {
  }
 
  fn apple_sdk_root(&self, sdk: &str) -> Result<OsString, Error> {
+ if let Some(sdkroot) = env::var_os("SDKROOT") {
+ return Ok(sdkroot);
+ }
+
  let mut cache = self
  .apple_sdk_root_cache
  .lock()