build: Apply libtool.patch at the last stage of configure.
* build-aux/libtool.patch: New. * build-aux/ltmain.sh: Revert our local change to original. * configure.ac [x86_64-*mingw32*] (libtool-patch): Introduce a construct with AC_CONFIG_COMMANDS to apply build-aux/libtool.patch after libtool generation.
- GnuPG-bug-id: T6619
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>