Provide rust-srpm-macros in RHEL
    
    rust-srpm-macros is a dependency of redhat-rpm-config so that Rust-based
    SRPMs can rely on these particular macros.  In RHEL 9 and earlier,
    rust-srpm-macros was a separate source package which was included in
    RHEL.  Since then, it became a subpackage of rust-packaging in Fedora.
    
    In order to not pull in any part of rust-packaging into RHEL 10, thereby
    allowing it to be maintained separately in EPEL, those macros are
    provided here instead.