add .ENOSYS == .Unsupported for posix too

core/os/os2/errors_posix.odin

@@ -26,6 +26,8 @@ _get_platform_error :: proc() -> Error {
 		return .Invalid_File
 	case .ENOMEM:
 		return .Out_Of_Memory
+	case .ENOSYS:
+		return .Unsupported
 	case:
 		return Platform_Error(errno)
 	}