Patch-Source: https://github.com/gentoo/gentoo/blob/dce914f2bbf52360f45c90d877857df3c4c2a353/app-arch/xar/files/xar-1.8.0.0.487-non-darwin.patch
--
don't do availability stuff on non-Darwin

--- a/include/xar.h.in
+++ b/include/xar.h.in
@@ -52,6 +52,7 @@
 #import <os/availability.h>
 #else
 #define API_DEPRECATED(...)
+#define API_AVAILABLE(...)
 #endif
 
 #pragma pack(4)
