fmsx: Fix build for Linux with XOrg dependency (#19541)
fmsx: Fix build for Linux with XOrg dependency (#19541)

https://github.com/Homebrew/linuxbrew-core/runs/434270743?check_suite_focus=true

```
2020-02-09T06:41:42.0796137Z X11 is required to install this formula,
either Xorg 1.12.2 or xdpyinfo 1.3.0, or newer. X11Requirement
unsatisfied!
2020-02-09T06:41:42.0796798Z You can install with Homebrew Cask:
2020-02-09T06:41:42.0797258Z   brew cask install xquartz
```
Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core,maxim-belkin/homebrew-core,rwhogg/homebrew-core