[Bug c/55105] New: use of LD_LIBRARY_PATH incorrect for AIX -- cause trunk build to fail

["pedzsan at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55105

             Bug #: 55105
           Summary: use of LD_LIBRARY_PATH incorrect for AIX -- cause
                    trunk build to fail
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pedzsan@gmail.com


configure.ac has this:

# Decide which environment variable is used to find dynamic libraries.
case "${host}" in
  *-*-hpux*) RPATH_ENVVAR=SHLIB_PATH ;;
  *-*-darwin*) RPATH_ENVVAR=DYLD_LIBRARY_PATH ;;
  *-*-mingw* | *-*-cygwin ) RPATH_ENVVAR=PATH ;;
  *) RPATH_ENVVAR=LD_LIBRARY_PATH ;;
esac

Starting with AIX 6.1, LD_LIBRARY_PATH is used.  I don't 100% understand the
intent of the code above.  The environment variable mentioned (e.g.
LD_LIBRARY_PATH) is passed via the environment when (e.g.) libatomic is built. 
With LD_LIBRARY_PATH in the environment, xgcc and cc1 no longer execute
properly because at the time they execute, LD_LIBRARY_PATH points to the bit
version being built -- not the bit version that xgcc was built for.  There is a
longer description here: http://gcc.gnu.org/ml/gcc/2012-10/msg00386.html

I changed it to this:

# Decide which environment variable is used to find dynamic libraries.
case "${host}" in
  *-*-aix*) RPATH_ENVVAR=BOGUS ;;
  *-*-hpux*) RPATH_ENVVAR=SHLIB_PATH ;;
  *-*-darwin*) RPATH_ENVVAR=DYLD_LIBRARY_PATH ;;
  *-*-mingw* | *-*-cygwin ) RPATH_ENVVAR=PATH ;;
  *) RPATH_ENVVAR=LD_LIBRARY_PATH ;;
esac

In theory, it should be "LIBPATH" but I'm sure that will cause the build to
fail as well.  In essence, the logic needs to be reviewed.  Perhaps other
platforms are different in their use of LD_LIBRARY_PATH / LIBPATH than AIX.