Fix out-of-tree build

The current AX_CONFIG_SUBDIR_OPTION macro assumes that $srcdir is a
relative path. If it is not, jimtcl/configure.gnu is generated such that
an out-of-tree build will fail at the configure step unless the build dir
is a sibling to the source dir.

Change the generated jimtcl/configure.gnu wrapper to use the same
`dirname $0` trick as jimtcl/configure (which itself is a wrapper around
autosetup).

Change-Id: I0fb19ae114ba37169b422b28313262f9bd83eb6f
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/1528
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-by: Xiaofan <xiaofanc@gmail.com>

config_subdir.m4

@@ -21,7 +21,6 @@ AC_DEFUN([AX_CONFIG_SUBDIR_OPTION],
 AC_CONFIG_SUBDIRS([$1])
 
 m4_ifblank([$2], [rm -f $srcdir/$1/configure.gnu],
-[printf "#!/bin/sh
-"\$"SHELL "../$srcdir/$1/configure" $2 \""\$"@"\" > "$srcdir/$1/configure.gnu"
+[echo -e '#!/bin/sh\nexec "`dirname "'\$'0"`/configure" $2 "'\$'@"' > "$srcdir/$1/configure.gnu"
 ])
 ])