Fix chrome/test/data/safe_browsing/dmg/generate_test_data.sh to not silently fail.

chrome/test/data/safe_browsing/dmg/generate_test_data.sh

 #!/bin/sh
 
 # Copyright 2015 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.
 
+set -eu
+
 THIS_DIR=$(dirname "$0")
 
 OUT_DIR="$1"
 
 if [[ ! "$1" ]]; then
   echo "Usage: $(basename "$0") [output_dir]"
   exit 1
 fi
 
 if [[ -e "$1" && ! -d "$1" ]]; then
   echo "Output directory \`$1' exists but is not a directory."
   exit 1
 fi
 if [[ ! -d "$1" ]]; then
   mkdir -p "$1"
 fi
 
 generate_test_data() {
+  # `hdiutil convert` cannot overwrite files, so remove items in the output
+  # directory.
+  rm -f "${OUT_DIR}"/*
+
   # HFS Raw Images #############################################################
 
   MAKE_HFS="${THIS_DIR}/make_hfs.sh"
   "${MAKE_HFS}" HFS+ 1024 "${OUT_DIR}/hfs_plus.img"
   "${MAKE_HFS}" hfsx $((8 * 1024)) "${OUT_DIR}/hfsx_case_sensitive.img"
 
   # DMG Files ##################################################################
 
   DMG_SOURCE=$(mktemp -d -t dmg_generate_test_data.XXXXXX)
   echo "This is a test DMG file. It has been generated from " \
       "chrome/test/data/safe_browsing/dmg/generate_test_data.sh" \
           > "${DMG_SOURCE}/README.txt"
-  dd if=/dev/urandom of="${DMG_SOURCE}/random" bs=512 count=4
+  dd if=/dev/urandom of="${DMG_SOURCE}/random" bs=512 count=4 &> /dev/null
 
   DMG_TEMPLATE_FORMAT="UDRO"
   DMG_FORMATS="UDRW UDCO UDZO UDBZ UFBI UDTO UDSP"
   DMG_LAYOUTS="SPUD GPTSPUD NONE"
 
   # First create uncompressed template DMGs in the three partition layouts.
   for layout in ${DMG_LAYOUTS}; do
     DMG_NAME="dmg_${DMG_TEMPLATE_FORMAT}_${layout}"
     hdiutil create -srcfolder "${DMG_SOURCE}" \
       -format "${DMG_TEMPLATE_FORMAT}" -layout "${layout}" \
       -volname "${DMG_NAME}" \
-      -ov "${OUT_DIR}/${DMG_NAME}"
+      "${OUT_DIR}/${DMG_NAME}"
   done
 
   # Convert each template into the different compression format.
   for format in ${DMG_FORMATS}; do
     for layout in ${DMG_LAYOUTS}; do
       TEMPLATE_NAME="dmg_${DMG_TEMPLATE_FORMAT}_${layout}.dmg"
       DMG_NAME="dmg_${format}_${layout}"
       hdiutil convert "${OUT_DIR}/${TEMPLATE_NAME}" \
         -format "${format}" -o "${OUT_DIR}/${DMG_NAME}"
     done
@@ skipping 13 matching lines @@
   mkdir "${DMG_SOURCE}/.hidden"
   cp "${THIS_DIR}/../mach_o/lib64.dylib" "${DMG_SOURCE}/.hidden/"
 
   hdiutil create -srcfolder "${DMG_SOURCE}" \
     -format UDZO -layout SPUD -volname "Mach-O in DMG" -ov \
     "${OUT_DIR}/mach_o_in_dmg"
 
   rm -rf "${DMG_SOURCE}"
 }
 
-# Silence any log output.
-generate_test_data &> /dev/null
+# Silence any stdout, but keep stderr.
+generate_test_data > /dev/null