AC_LIBTOOL_SYS_MAX_CMD_LEN and CONFIG_SHELL

[Kevin Ryde]

In AC_LIBTOOL_SYS_MAX_CMD_LEN I think $CONFIG_SHELL isn't always
available.

Both _LT_AC_PROG_ECHO_BACKSLASH and _AS_LINENO_PREPARE only set it
when they decide to reexec configure, and on ia64 hpux it turns out
that this doesn't happen (due to having "print -r" for echoing, and a
working $LINENO already in /bin/sh already).

The problem only shows up when running "sh configure".  If instead "sh
./configure" is used it ends up working because in that case an empty
$CONFIG_SHELL in

        $CONFIG_SHELL $0 --fallback-echo "X$testring"

comes out as a normal program run of "./configure --fallback-echo ...".

I think plain $SHELL would be sufficient, and is always set by
autoconf (to a user or reexec supplied $CONFIG_SHELL, or /bin/sh
otherwise).

        * config_shell/libtool.m4 (AC_LIBTOOL_SYS_MAX_CMD_LEN): Use $SHELL,
        since $CONFIG_SHELL is not always set.

libtool.m4.cmdlen.diff
Description: Source code patch