Upstream status: Not upstreamed.

The build system refuses to cross-compile for unknown targets
even though it works fine.  Add GNU/Hurd target.

--- Python-3.8.5/configure.orig	2020-10-26 14:06:09.665423525 +0100
+++ Python-3.8.5/configure	2020-10-26 14:08:30.987765738 +0100
@@ -3278,6 +3278,9 @@
 	*-*-vxworks*)
 	    ac_sys_system=VxWorks
 	    ;;
+	*-*-gnu)
+	    ac_sys_system=GNU
+	    ;;
 	*)
 		# for now, limit cross builds to known configurations
 		MACHDEP="unknown"
@@ -3328,6 +3331,9 @@
 	*-*-vxworks*)
 		_host_cpu=$host_cpu
 		;;
+	*-*-gnu)
+		_host_cpu=$host_cpu
+	    ;;
 	*)
 		# for now, limit cross builds to known configurations
 		MACHDEP="unknown"