Don't assume this is run from the chroot and point explicity to it.

src/scripts/enable_localaccount.sh

Index: src/scripts/enable_localaccount.sh
diff --git a/src/scripts/enable_localaccount.sh b/src/scripts/enable_localaccount.sh
index fc0a84eecd0fb7427230ca766d062b68cbf6ca4a..ea54b41af3cc510f5a6b4df58f2804d61ed9c6d4 100755
--- a/src/scripts/enable_localaccount.sh
+++ b/src/scripts/enable_localaccount.sh
@@ -6,10 +6,13 @@ set -e
 
 if [ -z $1 ]
 then
-  echo "Usage: $0 localaccount_username"
+  echo "Usage: $0 localaccount_username [chroot_path]"
   exit 1
 fi
 
+# Default chroot_path to its standard location
+chroot_path=${2:-"../../chroot"}
+
 echo "Enabling local account $1@gmail.com."
 echo "Remove these files to disable:"
 
@@ -36,10 +39,12 @@ EOF
 done
 
 # Add CHROMEOS_LOCAL_ACCOUNT var to /etc/make.conf.user
+echo "Setting CHROMEOS_LOCAL_ACCOUNT in $chroot_path/etc/make.conf.user..."
 VAR_NAME=CHROMEOS_LOCAL_ACCOUNT
-if grep -q ${VAR_NAME} /etc/make.conf.user; then
+if grep -q ${VAR_NAME} $chroot_path/etc/make.conf.user; then
    regex="s/${VAR_NAME}=.*/${VAR_NAME}=$1@gmail.com/"
-   sudo sed -i -e "${regex}"  /etc/make.conf.user
+   sudo sed -i -e "${regex}"  $chroot_path/etc/make.conf.user
 else
-   sudo sh -c "echo ""${VAR_NAME}=$1@gmail.com"" >> /etc/make.conf.user"
+   sudo sh -c "echo ""${VAR_NAME}=$1@gmail.com"" >> \
+               $chroot_path/etc/make.conf.user"
 fi