pkg-config package is named differently on supported rpm-based systems:
- Amazon Linux 2 has pkgconfig
- Fedora has pkgconf-pkg-config
- RHEL 7 has pkgconfig
- RHEL 8 and 9 have pkgconfig-pkg-config
What they share in common is they all provide 'pkgconfig', which we can
use in the spec file so we don't have to specify it per-OS.
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