Different CFLAGS for `cpu_features` about dump1090 HOT 1 CLOSED

Makefile.cpufeatures is basically there to avoid having to run a cmake build of cpu_features and then try to work out where it put everything. The cflags are different because cpu_features is a third-party library with its own compile requirements that don't necessarily line up with the main dump1090 cflags.

The eventual solution (probably) to move everything to cmake, but that is a larger project than I wanted to take on right now. Then you can do whatever you need to do for cmake globally.

For now, if you need to inject additional flags, you'll need to inject them into CPUFEATURES_CFLAGS too

from dump1090.