Bug#979066: mangohud: Build fails on buster

[Stephan Lachnit]

Control: tags -1 wontfix buster

Thanks for reporting this, and thanks Stephen for looking into it.
I won't fix this since I never planned to support buster with this
package, especially since bullseye is just around the corner. If
the Vulkan backport works, that's nice, but please don't file bugs
regarding buster support, I won't test if it works on buster.

Regards,
Stephan Lachnit