[Bug bootstrap/77661] New: --enable-maintainer-mode causes in-tree-build of MPC to fail

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77661

            Bug ID: 77661
           Summary: --enable-maintainer-mode causes in-tree-build of MPC
                    to fail
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: build
          Severity: normal
          Priority: P3
         Component: bootstrap
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org
  Target Milestone: ---

Compiling GCC with in-tree MPC (+ mpfr + gmp + ISL) fails with
--enable-maintainer-mode as the latter also updates the configure scripts of
those.

In particular, the in-tree-build of MPC fails with:

make[3]: Entering directory `build/mpc'
(CDPATH="${ZSH_VERSION+.}:" && cd ../../mpc && /bin/sh mpc/missing autoheader)
aclocal.m4:17: warning: this file was generated for autoconf 2.69.
You have another version of autoconf.  It may work, but is not guaranteed to.
If you have problems, you may need to regenerate the build system entirely.
To do so, use the procedure documented by the package, typically 'autoreconf'.
configure.ac:27: error: Autoconf version 2.65 or higher is required
aclocal.m4:497: AM_INIT_AUTOMAKE is expanded from...
configure.ac:27: the top level
autom4te: m4 failed with exit status: 63
autoheader: 'autom4te' failed with exit status: 63
WARNING: 'autoheader' is probably too old.
         You should only need it if you modified 'acconfig.h' or
         'configure.ac' or m4 files included by 'configure.ac'.
         The 'autoheader' program is part of the GNU Autoconf package:
         <http://www.gnu.org/software/autoconf/>
         It also requires GNU m4 and Perl in order to run:
         <http://www.gnu.org/software/m4/>
         <http://www.perl.org/>
make[3]: *** [../../mpc/config.h.in] Error 63
make[3]: Leaving directory `build/mpc'