Require specific gettext version, as otherwise using
>=sys-devel/gettext-0.23 may lead to a build error due
to misaligned gettext versions.
https://bugs.gentoo.org/945976

--- a/configure.ac
+++ b/configure.ac
@@ -52,7 +52,7 @@ AC_TYPE_SIZE_T
 # i18n / text translations
 # The choice for version of gettext is only based on what was installed on the developers desktop (2021).
 # If another version is more convenient, go for it.
-AM_GNU_GETTEXT_VERSION([0.21])
+AM_GNU_GETTEXT_REQUIRE_VERSION([0.21])
 AM_GNU_GETTEXT([external])
 
 GETTEXT_PACKAGE="$PACKAGE"