[Discuss-gnuradio] VRT breaks build on non-Linux OSs

[Michael Dickens]

Since VRT seems to be currently linux-only (per the header "linux/ 
if_packet.h"), could someone put a check in the config/grc_vrt.m4  
script to check specifically for Linux & disables otherwise (al la:  
grc_usrp2.m4)?  [The AC_CHECK_HEADERS for that header in the m4 script  
isn't good enough since it just sets a #define (or doesn't set it),  
but doesn't provide configure with feedback as to the success or  
failure of finding and using that header.]

For now, non-Linux folks can disable VRT via the configure flag "-- 
disable-vrt". - MLD