GUI issues on GRC on macOS

[Mehdi Asgari]

Hello everyone. 
I have been trying to compile 3.8 on the latest version of macOS. Finally I 
managed to fix all the compile-time and runtime issues.
I can confirm that the runtime and GRC are working to some extent (for example 
by connecting a source to a waterfall sink and running the flow-graph 
flawlessly)
But now on “gnuradio-companion”, all the sub-menu items have a single icon: a 
grey display shaped icon. This is not a big issue to me, as I still can read 
the tooltips and find the buttons/items, but there are some other UI related 
problems as well.

For example when I try to open the filter design tool by going to the “Tools -> 
Filter Design Tool” menu, nothing happens. I just get this error in the command 
line:

```
/usr/local/Cellar/python/3.7.5/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py:883:
 ResourceWarning: subprocess 36222 is still running
 ResourceWarning, source=self)
ResourceWarning: Enable tracemalloc to get the object allocation traceback
```

But there’s no such sub-process running (in this case PID 36222)

Here’s my build info if it helps:
GNURadio 3.8.0 built from the release zip file
QWT 6.1.4
QT 5.12.6
Python 3.7.5

Any ideas?
Thanks in advance
Mehdi