[Bug libfortran/48664] New: Use autoconf test instead of target blacklist to determine weak undefined reference support

[jb at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48664

           Summary: Use autoconf test instead of target blacklist to
                    determine weak undefined reference support
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jb@gcc.gnu.org


As discussed in comments #48 and #49 in PR 47571, we should use a proper
autoconf test to figure out whether a target supports weak undefined references
instead of the current target blacklist in acinclude.m4.

It might be possible to use gcc/testsuite/gcc.dg/attr-weakref-1.c as a basis
for such an autoconf test.