Cleanups from post-submit suggestions.

build/linux/dump_app_syms

 #!/bin/sh
 
 # Copyright (c) 2009 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.
 #
 # Helper script to run dump_syms on Chrome Linux executables and "fixup" the
 # generated sigs (due to changes to the binary from stripping).
 
 set -e
 
 usage() {
-  echo "$0 <dump_syms_exe> <binary_with_symbols> <symbols_output>"
+  echo "$0 <dump_syms_exe> <binary_with_symbols> <symbols_output>" >&2
 }
 
 
 if [ $# -ne 3 ]; then
   usage
   exit 1
 fi
 
 SCRIPTDIR="$(readlink -f "$(dirname "$0")")"
 DUMPSYMS="$1"
 INFILE="$2"
 OUTFILE="$3"
 
 STRIPPED=$(mktemp -q -t stripped-XXXXX)
 if [ $? -ne 0 ]; then
-  echo "ERROR: Could not create temp stripped '$INFILE'"
+  echo "ERROR: Could not create temp stripped '$INFILE'" >&2
   exit 1
 fi
 
 # Dump the symbols from the given binary.
-"$DUMPSYMS" "$INFILE" > "$OUTFILE"
+if [ "$INFILE" -nt "$OUTFILE" ]; then
+  "$DUMPSYMS" "$INFILE" > "$OUTFILE"
+fi
 
 # Strip the binary and calculate the signature of that, since that's what ships.
 strip "$INFILE" -o "$STRIPPED"
 NEWSIG=$("$SCRIPTDIR/dump_signature.py" "$STRIPPED")
 rm "$STRIPPED"
 
 # Replace the old signature with the stripped signature in the symbols file.
-INFILE_BASE=$(basename "$INFILE")
-sed -i "1s/[0-9A-F]* $INFILE_BASE/$NEWSIG $INFILE_BASE/" "$OUTFILE"
-
+sed -i "1s/ [0-9A-F]* / $NEWSIG /" "$OUTFILE"