Use autoconf2.7x

RHEL-9 does not have autoconf-2.69, while configure.ac requires at least
2.71. Use a seperately packaged autoconf2.7x.

(It's possible to port configure.ac to older autoconf, but it would
require to carry a downstream-only patch.)

indent.spec

@@ -112,7 +112,7 @@ Source1:    https://ftpmirror.gnu.org/%{name}/%{name}-%{version}.tar.xz.sig
 # <https://blog.shadura.me/2021/01/01/new-openpgp-key/> and
 # <https://contributors.debian.org/contributor/andrewsh/>.
 Source2:    https://shadura.me/key.pgp
-BuildRequires:  autoconf >= 2.71
+BuildRequires:  autoconf2.7x >= 2.71
 # autoconf-archive for unbundled ax_cc_for_build.m4
 BuildRequires:  autoconf-archive
 BuildRequires:  automake
@@ -149,7 +149,7 @@ rm -r aclocal.m4 config configure m4 {,doc/,src/,man/}Makefile.in \
     po/Makefile.in.in po/*.sed po/*.sin po/Rules-quot
 
 %build
-autoreconf -i -f
+autoreconf27 -i -f
 %configure \
     --enable-largefile \
     --enable-nls \