debian/rules: Disable FFmpeg and GSM on Ubuntu
debian/rules: Disable FFmpeg and GSM on Ubuntu

Closes: #880157

bmiklautz/debian-freerdp2,bmiklautz/debian-freerdp2,bmiklautz/debian-freerdp2,bmiklautz/debian-freerdp2,bmiklautz/debian-freerdp2,bmiklautz/debian-freerdp2