[Bug libobjc/78697] New: --with-target-bdw-gc-include shouldn't be required to be per multilib

["ro at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78697

            Bug ID: 78697
           Summary: --with-target-bdw-gc-include shouldn't be required to
                    be per multilib
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libobjc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ro at gcc dot gnu.org
                CC: doko at gcc dot gnu.org
  Target Milestone: ---

When trying to use the new --with-target-bdw-gc-* options with an external
build
of gc 7.6.0 on Solaris/SPARC, Solaris/x86, and Linux/x86_64 (each with 32-bit
and
64-bit multilibs), I ran into the following error when configuring with

--with-target-bdw-gc-include=/vol/gcc/include

while ...-gc-lib had two multilibs:

checking for bdw garbage collector... using paths configured with
--with-target-bdw-gc options
configure: error: no multilib path (amd64) found in
--with-target-bdw-gc-include

Requiring those include paths to be specified explicitly makes no sense: the
directories are identical between 32 and 64-bit builds and the different
Solaris
and Linux trees, so one should be able to get away with a single

--with-target-bdw-gc-include

for one shared include dir.  Of course, having different ones for whatever
reason
should still be an option, just not a hard requirement.

  Rainer