Use the compiler to find libftdi

The libfdti detection, using ldconfig, only searches for the build
architecture libftdi, which means infnoise can't be cross-compiled.
By checking whether the compiler knows about the library we can
check for the host architecture's library and support build scenarios
which ldconfig doesn't know about, in particular cross-building.

software/Makefile.linux

@@ -10,7 +10,7 @@ CFLAGS = -Wall -Wextra -Werror -std=c99 -O3 -fPIC -I Keccak -I /usr/include/libf
  -DGIT_DATE=\"$(GIT_DATE)\"\
  -DLINUX
 
-FOUND = $(shell /sbin/ldconfig -p | grep --silent libftdi.so && echo found)
+FOUND = $(shell $(CC) -o /dev/null -x c /dev/null -shared -lftdi 2>/dev/null && echo found)
 ifeq ($(FOUND), found)
         FTDI=   -lftdi
 else