Improve gcore shell quoting and portability

The gcore shell script (gdb/gcore.in) doesn't quote its variables
enough.

For example, trying to write a core file with - say - a space
ungraciously fails like this:

    $ gcore -o 'foo bar' 6270
    /usr/bin/gcore: line 92: [: foo: binary operator expected
    gcore: failed to create foo bar.6270

Similarly, one can inject meta characters like * (by accident)
that may yield unexpected results, e.g. as in:

    $ gcore -o foobar '*'

This change fixes these issues in several places.

Aso, since the script uses array syntax, the patch changes the
the shell in the first line from `/bin/sh` to /bin/bash`.

POSIX doesn't specify the array syntax for shell, thus, the
script doesn't work on systems where /bin/sh is linked to - say -
dash.

Since the source gcore.in already is processed by a pre-processor
one could even auto-detect the path to bash and thus dynamically
generate the first line. For systems where bash isn't available
via /bin/bash. But I think this would be overkill and /bin/bash
is good enough as most systems probably have it.

gdb/ChangeLog:

	PR gdb/22888
	* gcore.in: Quote variables and switch interpreter to bash.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2018-03-01  Georg Sauthoff  <mail@georg.so>
+
+	PR gdb/22888
+	* gcore.in: Quote variables and switch interpreter to bash.
+
 2018-03-01  Tom Tromey  <tom@tromey.com>
 
 	* dwarf2read.c (alloc_discriminant_info): Fix default_index

gdb/gcore.in

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 #   Copyright (C) 2003-2018 Free Software Foundation, Inc.
 
@@ -28,9 +28,9 @@ name=core
 dump_all_cmds=()
 
 while getopts :ao: opt; do
-    case $opt in
+    case "$opt" in
         a)
-            case $OSTYPE in
+            case "$OSTYPE" in
                 linux*)
                     dump_all_cmds=("-ex" "set use-coredump-filter off")
                     dump_all_cmds+=("-ex" "set dump-excluded-mappings on")
@@ -84,7 +84,7 @@ fi
 
 # Check if the GDB binary is in the expected path.  If not, just
 # quit with a message.
-if [ ! -f "$binary_path"/@GDB_TRANSFORM_NAME@ ]; then
+if [ ! -f "$binary_path/@GDB_TRANSFORM_NAME@" ]; then
   echo "gcore: GDB binary (${binary_path}/@GDB_TRANSFORM_NAME@) not found"
   exit 1
 fi
@@ -93,16 +93,16 @@ fi
 rc=0
 
 # Loop through pids
-for pid in $*
+for pid in "$@"
 do
 	# `</dev/null' to avoid touching interactive terminal if it is
 	# available but not accessible as GDB would get stopped on SIGTTIN.
-	$binary_path/@GDB_TRANSFORM_NAME@ </dev/null --nx --batch \
+	"$binary_path/@GDB_TRANSFORM_NAME@" </dev/null --nx --batch \
 	    -ex "set pagination off" -ex "set height 0" -ex "set width 0" \
 	    "${dump_all_cmds[@]}" \
 	    -ex "attach $pid" -ex "gcore $name.$pid" -ex detach -ex quit
 
-	if [ -r $name.$pid ] ; then 
+	if [ -r "$name.$pid" ] ; then
 	    rc=0
 	else
 	    echo "@GCORE_TRANSFORM_NAME@: failed to create $name.$pid"