Add RPM spec file for Fedora, CentOS, RedHat

This RPM spec file allows us to build RPMs for Fedora, CentOS, and RedHat using the openSUSE Build Service. The build for openSUSE fails because the one package produced bundles both shared libraries and binaries. I believe there is also a problem with the library SO name, which I'll look into later.

The packages are currently pushed into the `home:mgeisler` project there. I believe we can ask for a proper `zerovm` project later if we want.