Handle Void Linux detection. From upstream https://github.com/void-linux/void-packages/blob/2fd8d4df94855a157a4de16c61d54153e16ef185/srcpkgs/os-prober/patches/detect-void.patch

Bug: https://bugs.gentoo.org/817905

--- a/os-probes/mounted/common/90linux-distro
+++ b/os-probes/mounted/common/90linux-distro
@@ -116,6 +116,13 @@
 	elif [ -e "$dir/sbin/pkgtool" ]; then
 		short="Slackware"
 		long="Slackware Linux"
+	elif [ -e "$dir/sbin/xbps-install" ]; then
+		short="Void"
+		if file "$dir/sbin/xbps-install"|grep -q 32-bit; then
+			long="Void Linux 32"
+		else
+			long="Void Linux 64"
+		fi
 	elif grep -qs OpenLinux "$dir/etc/issue"; then
 		short="Caldera"
 		long="Caldera OpenLinux"