dev-libs/libgdata: fix build with newer autoconf-archive present
Workaround eaclocal overwriting the older ax_code_coverage.m4
provided by the tarball, stopping breakage when newer autoconf-archive
is present on the system.
Due to all necessary ax_*.m4 being present in the tarball, the
autoconf-archive build dep is also unnecessary (and now it doesn't
update the copies either anymore if it's present on the build system).
Closes: https://bugs.gentoo.org/686082
Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: Mart Raudsepp <leio@gentoo.org>