build: allow for local gnulib diffs

Commit f7bd00c12 pulled in a gnulib module that fails to compile
on mingw.  While it would be nice to pull in a newer version of
.gnulib that fixes this, it is difficult to backport any .gnulib
update to older releases.  So, it makes sense to take advantage
of gnulib-tool's ability to support local diffs, where we can
apply specific diffs in our use of gnulib without waiting for
upstream gnulib to pick up those changes, as well as avoiding
a wholesale .gnulib update.  The existence of local diffs will
also make it easier to backport fixes against a tarball (as long
as a tarball and libvirt.git share the same .gnulib commit, then
the tarball can be patched by applying the same local diffs as
a post-release libvirt.git commit, without having to rerun an
entire gnulib-tool bootstrap).

This patch introduces the framework for supporting local diffs,
without actually introducing any.

* bootstrap.conf (local_gl_dir): New variable.
* autogen.sh (bootstrap_hash): Hash any local diffs, to force a
re-bootstrap if just diffs change.
* cfg.mk (_update_required): Likewise.

1 files changed, 4 insertions, 2 deletions

diff --git a/bootstrap.conf b/bootstrap.conf
index 4557d2da9..6498aba50 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -160,9 +160,10 @@ fi
 
 # Tell gnulib to:
 #   require LGPLv2+
+#   apply any local diffs in gnulib/local/ dir
 #   put *.m4 files in new gnulib/m4/ dir
-#   put *.[ch] files in new gnulib/lib/ dir.
-#   import gnulib tests in new gnulib/tests/ dir.
+#   put *.[ch] files in new gnulib/lib/ dir
+#   import gnulib tests in new gnulib/tests/ dir
 gnulib_name=libgnu
 m4_base=gnulib/m4
 source_base=gnulib/lib
@@ -172,6 +173,7 @@ gnulib_tool_option_extras="\
  --with-tests\
  --avoid=pt_chown\
 "
+local_gl_dir=gnulib/local
 
 # Convince bootstrap to use multiple m4 directories.
 : ${ACLOCAL=aclocal}