Building usb audio sample hangs the pre-processor

[arvid-r]

Describe the bug
When trying to build the headset usb audio sample, the build process hangs with 100% cpu usage and never seems to finish.

To Reproduce
Steps to reproduce the behavior:

1. checkout zephyr and cd into directory
2. west -v build -p auto -b nrf52840dk_nrf52840 samples/subsys/usb/audio/headset
3. won't finish ...

Expected behavior
Build should finish shortly, and the sample should run on the selected board

Impact
Showstopper for USB audio subsystem

Environment (please complete the following information):

• OS: MacOS
• gcc-arm-none-eabi-9-2019-q4-major
• Commit SHA or Version used: ed2d263

Additional context
The pre-processor gets stuck with audio.c open, and the problem goes away if you comment out the following lines:

UTIL_LISTIFY(HEADPHONES_DEVICE_COUNT, HEADPHONES_DEVICE, HP)
UTIL_LISTIFY(MICROPHONE_DEVICE_COUNT, MICROPHONE_DEVICE, MIC)
UTIL_LISTIFY(HEADSET_DEVICE_COUNT, HEADSET_DEVICE, HS)

So this probably has something to do with macro expansion and the devicetree

[eobalski]

I am observing same with my setup. I am using vm linux. Something was merged in between what broke the build. I am investigating the issue.

[eobalski]

Got the fix, will prepare a PR asap.