From Fedora Project Wiki
Proposal to add other macro for compatibility, when needed
%{!?_httpd_apxs: %{expand: %%global _httpd_apxs %%{_sbindir}/apxs}}
%{!?_httpd_mmn: %{expand: %%global _httpd_mmn %%(cat %{_includedir}/httpd/.mmn || echo missing-httpd-devel)}}
%{!?_httpd_confdir: %{expand: %%global _httpd_confdir %%{_sysconfdir}/httpd/conf.d}}
%{!?_httpd_modconfdir: %{expand: %%global _httpd_modconfdir %%{_sysconfdir}/httpd/conf.d}}
%{!?_httpd_moddir: %{expand: %%global _httpd_moddir %%{_libdir}/httpd/modules}}
Note than _httpd_modconfdir, like _httpd_apxs will have different value on httpd 2.2 and 2.4