hpux cc +Z warning

[Kevin Ryde]

I had the misfortune to try cvs libtool on hppa2.0-hp-hpux10.20 with a
version of the unbundled cc that prints the following warning when +O3
is used with +Z,

        cc: warning 8006: Do not use optimization levels higher than 2 to 
generate a shared library if a user of that library may redefine a routine 
within that library (8006)

Alas that warning makes AC_LIBTOOL_COMPILER_OPTION decide +Z is no
good.

If AC_LIBTOOL_COMPILER_OPTION just wants to know if the option is
accepted, then perhaps it could grep for it in the output, on the
assumption "Unknown option: -foo" or similar would result from a bad
one.  That would avoid being tricked by informational messages, or
even perhaps by compiler advertising banners.

By way of a concrete suggestion,

        * libtool.m4 (AC_LIBTOOL_COMPILER_OPTION): Look for the name
        of the option in the output before rejecting it.

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