expr isn't on the ramdisk use ksh for addition

problem spotted by jasper@

diff --git a/distrib/armv7/ramdisk/install.md b/distrib/armv7/ramdisk/install.md
index deebc18..2ae7c70 100644 (file)
--- a/distrib/armv7/ramdisk/install.md
+++ b/distrib/armv7/ramdisk/install.md
@@ -1,4 +1,4 @@
-#      $OpenBSD: install.md,v 1.14 2015/06/08 17:35:43 jsg Exp $
+#      $OpenBSD: install.md,v 1.15 2015/06/08 18:31:17 jsg Exp $
 #
 #
 # Copyright (c) 1996 The NetBSD Foundation, Inc.
@@ -136,7 +136,7 @@ md_prep_fdisk() {
        if [[ -n $CUBOX ]]; then
                bootsectorstart="2048"
        fi
-       bootsectorend=`expr $bootsectorstart + $bootsectorsize`
+       bootsectorend=$(($bootsectorstart + $bootsectorsize))
 
        while :; do
                _d=whole