bug#14991: distcheck passes --prefix to configure before *DISTCHECK_CONFIGURE_FLAGS

[Akim Demaille]

Hi!

Admittedly, what prompts this report is arguably a bug in
a package: It passes _all_ the configure flags to
AM_DISTCHECK_CONFIGURE_FLAGS.  Not a bright idea I guess,
but simple.

Unfortunately distcheck reads:

# This target untars the dist file and tries a VPATH configuration.  Then
# it guarantees that the distribution is self-contained by making another
# tarfile.
distcheck: dist
        case '$(DIST_ARCHIVES)' in \
        *.tar.gz*) \
…
          && ../configure --srcdir=.. --prefix="$$dc_install_base" \
            $(AM_DISTCHECK_CONFIGURE_FLAGS) \
            $(DISTCHECK_CONFIGURE_FLAGS) \
          && $(MAKE) $(AM_MAKEFLAGS) \

So the "local" flags, --srcdir and especially --prefix, are
provided by distcheck, and then overridden by the user's
DISTCHECK_CONFIGURE_FLAGS.  Since I use --prefix, boom.

Very much agreed, --prefix should not have made it into
(AM_)DISTCHECK_CONFIGURE_FLAGS; however it seems simple to
just pass --srcdir and --prefix last to be protected against
such cases.

Thanks!