Report better error message on update sandbox for gn builds

build/update-linux-sandbox.sh

 #!/bin/sh
 
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 BUILDTYPE="${BUILDTYPE:-Debug}"
 CHROME_SRC_DIR="${CHROME_SRC_DIR:-$(dirname -- $(readlink -fn -- "$0"))/..}"
 CHROME_OUT_DIR="${CHROME_SRC_DIR}/${CHROMIUM_OUT_DIR:-out}/${BUILDTYPE}"
 CHROME_SANDBOX_BUILD_PATH="${CHROME_OUT_DIR}/chrome_sandbox"
@@ skipping 21 matching lines @@
   return $?
 }
 
 if [ ! -d "${CHROME_OUT_DIR}" ]; then
   echo -n "${CHROME_OUT_DIR} does not exist. Use \"BUILDTYPE=Release ${0}\" "
   echo "If you are building in Release mode"
   exit 1
 fi
 
 if [ ! -f "${CHROME_SANDBOX_BUILD_PATH}" ]; then
-  echo -n "Could not find ${CHROME_SANDBOX_BUILD_PATH}, "
-  echo "please make sure you build the chrome_sandbox target"
+  echo "Could not find ${CHROME_SANDBOX_BUILD_PATH}"
+  echo -n "BUILDTYPE is $BUILDTYPE, use \"BUILDTYPE=<value> ${0}\" to override "
+  echo "after you build the chrome_sandbox target"
   exit 1
 fi
 
 if [ ! -f "${CHROME_SANDBOX_INST_PATH}" ]; then
   echo -n "Could not find ${CHROME_SANDBOX_INST_PATH}, "
   echo "installing it now."
   installsandbox
 fi
 
 if [ ! -f "${CHROME_SANDBOX_INST_PATH}" ]; then
@@ skipping 12 matching lines @@
   fi
 else
   echo "Your setuid sandbox is up to date"
   if [ "${CHROME_DEVEL_SANDBOX}" != "${CHROME_SANDBOX_INST_PATH}" ]; then
     echo -n "Make sure you have \"export "
     echo -n "CHROME_DEVEL_SANDBOX=${CHROME_SANDBOX_INST_PATH}\" "
     echo "somewhere in your .bashrc"
     echo "This variable is currently: ${CHROME_DEVEL_SANDBOX:-empty}"
   fi
 fi