Fix build when no libusb-LA is compiled.
-rw-r--r-- 1162 Makefile.am
-rw-r--r-- 10419 decode.c
drwxr-xr-x - decoders
-rw-r--r-- 295 libsigrokdecode.pc.in
-rw-r--r-- 2702 sigrokdecode.h