Allow cross-compilation on macOS

Author: zanieb

configure

@@ -330,6 +330,9 @@ then
 	*-apple-ios*)
 		ac_sys_system=iOS
 		;;
+	*-*-darwin*)
+		ac_sys_system=Darwin
+		;;
 	*-*-vxworks*)
 	    ac_sys_system=VxWorks
 	    ;;
@@ -790,6 +793,15 @@ if test "$cross_compiling" = yes; then
 				;;
 		esac
 		;;
+	*-*-darwin*)
+		case "$host_cpu" in
+		arm*)
+			_host_ident=arm
+			;;
+		*)
+			_host_ident=$host_cpu
+		esac
+		;;
 	*-*-vxworks*)
 		_host_ident=$host_cpu
 		;;