RPM package built on Mac OS fails to install on CentOS

[bertfrees]

I get the error:

package ... is intended for a different operating system

The fact that I can build the webui RPM package on my Mac and install it on CentOS proves that it is possible. My guess is that something is missing from the rpmbuild configuration.

My version of rpmbuild is 5.4.15.

P.S.: This issue isn't a huge inconvenience because I can build RPMs on a CentOS virtual machine or Docker container, but it would be nice if I can just do it from my native OS.

[bertfrees]

@alaram @joeha480 FYI