Adding required graphics libraries.
Adding required graphics libraries.

```
-- VPR Graphics: Disabled (required libraries missing, on debia/ubuntu try: sudo apt install libgtk-3 libx11-dev
```

```
Failed to find Qt5Widgets required for blifexplorer (on debian/ubuntu try
  'sudo apt install qt5-default')
```

Signed-off-by: Tim 'mithro' Ansell <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@mith.ro>

SymbiFlow/vtr-verilog-to-routing-kokoro