Use fxx-build/latest/src repo instead of fetching headers from koji

[ignatenkobrain]

None of Rust packages now correctly rebuild in Rust because it does not see the dynamic BuildRequires generated during the build.

But if you switch to using build repo, then everything should be there:

❯ sudo dnf --enablerepo=koji,koji-source repoquery --arch src --requires rust-starship 
Last metadata expiration check: 0:00:07 ago on Tue 03 Mar 2020 06:16:03 AM CET.
(crate(ansi_term/default) >= 0.12.1 with crate(ansi_term/default) < 0.13.0)
(crate(battery/default) >= 0.7.5 with crate(battery/default) < 0.8.0)
(crate(byte-unit/default) >= 3.0.3 with crate(byte-unit/default) < 4.0.0)
(crate(chrono/default) >= 0.4.0 with crate(chrono/default) < 0.5.0)
(crate(clap/default) >= 2.33.0 with crate(clap/default) < 3.0.0)
(crate(dirs/default) >= 2.0.2 with crate(dirs/default) < 3.0.0)
(crate(gethostname/default) >= 0.2.1 with crate(gethostname/default) < 0.3.0)
(crate(git2) >= 0.11.0 with crate(git2) < 0.12.0)
(crate(log/default) >= 0.4.8 with crate(log/default) < 0.5.0)
(crate(nom/default) >= 5.1.0 with crate(nom/default) < 6.0.0)
(crate(once_cell/default) >= 1.3.1 with crate(once_cell/default) < 2.0.0)
(crate(open/default) >= 1.3.4 with crate(open/default) < 2.0.0)
(crate(os_info/default) >= 2.0.0 with crate(os_info/default) < 3.0.0)
(crate(path-slash/default) >= 0.1.1 with crate(path-slash/default) < 0.2.0)
(crate(pretty_env_logger/default) >= 0.4.0 with crate(pretty_env_logger/default) < 0.5.0)
(crate(rayon/default) >= 1.3.0 with crate(rayon/default) < 2.0.0)
(crate(reqwest/blocking) >= 0.10.1 with crate(reqwest/blocking) < 0.11.0)
(crate(reqwest/default) >= 0.10.1 with crate(reqwest/default) < 0.11.0)
(crate(serde_json/default) >= 1.0.48 with crate(serde_json/default) < 2.0.0)
(crate(starship_module_config_derive/default) >= 0.1.0 with crate(starship_module_config_derive/default) < 0.2.0)
(crate(sysinfo/default) >= 0.11.2 with crate(sysinfo/default) < 0.12.0)
(crate(tempfile/default) >= 3.1.0 with crate(tempfile/default) < 4.0.0)
(crate(term_size/default) >= 0.3.1 with crate(term_size/default) < 0.4.0)
(crate(textwrap/default) >= 0.11.0 with crate(textwrap/default) < 0.12.0)
(crate(toml/default) >= 0.5.6 with crate(toml/default) < 0.6.0)
(crate(unicode-segmentation/default) >= 1.6.0 with crate(unicode-segmentation/default) < 2.0.0)
(crate(unicode-width/default) >= 0.1.7 with crate(unicode-width/default) < 0.2.0)
(crate(urlencoding/default) >= 1.0.0 with crate(urlencoding/default) < 2.0.0)
(crate(yaml-rust/default) >= 0.4.0 with crate(yaml-rust/default) < 0.5.0)
git-core
rust-packaging

[mizdebsk]

In Fedora Koji generation of "src" repos is enabled only for rawhide (f33-build tag). Therefore Koschei can't use "src" repos for all collections. I'm not in favour of maintaining 2 different ways of getting build requires.