Just went to build the dev variant of the unix port and got this error:

CC ../../lib/btstack/src/ad_parser.c
error: unknown warning option '-Wimplicit-fallthrough=0'; did you mean '-Wimplicit-fallthrough'? [-Werror,-Wunknown-warning-option]
make: *** [build-incident/lib/btstack/src/ad_parser.o] Error 1

Building on: macOS 10.15.7 (19H1217)
From commit: 8be29b9

I modified the file extmod/btstack/btstack.mk to omit the offending option entirely and was able to proceed through a successful build. No warnings were generated.

I understand this flag was added recently (#6578). Could this be a linux vs. osx issue?