Use `%bcond` macro for conditional builds in the spec file

[vashirov]

Issue Description
rpmbuild supports conditional package builds with the command line switches --with and --without:
https://rpm-software-management.github.io/rpm/manual/conditionalbuilds.html

This is useful to rebuild an existing src.rpm file without editing the spec file first. Or build in COPR with macros overrides for some options. For example, automatic rebuilds from dist-git in COPR to produced sanitized builds.

We use our custom global variables for different options such as use_cockpit or use_asan. Instead we should switch to %bcond macro.