enter_chroot.sh: mount configfs

DevServer will need configfs mounted inside chroot to be able to
create/manipulate iSCSI targets.

BUG=chromium:570766
TEST=`cros_sdk --enter` works, configfs is mounted inside chroot.

Change-Id: I7f7f8dfa4fcf4a062c2378f212b99fddd48bc22b
Reviewed-on: https://chromium-review.googlesource.com/343572
Commit-Ready: Victor Dodon <printesoi@chromium.org>
Tested-by: Victor Dodon <printesoi@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/sdk_lib/enter_chroot.sh b/sdk_lib/enter_chroot.sh
index c0dc589..5799092 100755
--- a/sdk_lib/enter_chroot.sh
+++ b/sdk_lib/enter_chroot.sh
@@ -285,6 +285,9 @@
     if grep -q binfmt_misc /proc/filesystems; then
       setup_mount binfmt_misc "-t binfmt_misc" /proc/sys/fs/binfmt_misc
     fi
+    if grep -q configfs /proc/filesystems; then
+      setup_mount none "-t configfs" /sys/kernel/config
+    fi
     setup_mount /dev "--bind" /dev
     setup_mount /dev/pts "--bind" /dev/pts
     if [[ -d /run ]]; then