Fixes build failure as seen in CI:
autoreconf: running: /usr/bin/autoconf --force
configure.ac:43: error: possibly undefined macro: AC_DISABLE_STATIC
If this token and others are legitimate, please use m4_pattern_allow.
See the Autoconf documentation.
configure.ac:44: error: possibly undefined macro: AC_PROG_LIBTOOL
autoreconf: error: /usr/bin/autoconf failed with exit status: 1
(I believe this is showing up now because changes in the gitlab.fd.o infrastructure caused us to regenerate the build containers, and somehow this time libtool wasn't picked up as an automatic dependency of the other packages in the container as it previously had been.)