fix missing defines

CMakeLists.txt

@@ -73,8 +73,8 @@ check_function_exists(ppoll HAVE_PPOLL)
 check_include_file(linux/serial.h HAVE_LINUX_SERIAL -DHAVE_LINUX_SERIAL=1)
 check_include_file(dev/usb/uftdiio.h HAVE_FREEBSD_UFTDI -DHAVE_FREEBSD_UFTDI=1)
 
-check_function_exists(argp_parse HAVE_ARGP)
-if(NOT HAVE_ARGP)
+check_function_exists(argp_parse HAVE_ARGP_H)
+if(NOT HAVE_ARGP_H)
   if(NOT ARGP_HINTS)
     set(ARGP_HINTS ~/argp-standalone/src)
   endif(NOT ARGP_HINTS)
@@ -83,7 +83,7 @@ if(NOT HAVE_ARGP)
     message(FATAL_ERROR "argp library not available")
   endif(NOT LIB_ARGP)
   set(CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES} ${LIB_ARGP}")
-endif(NOT HAVE_ARGP)
+endif(NOT HAVE_ARGP_H)
 
 option(coverage "enable code coverage tracking." OFF)
 if(NOT coverage STREQUAL OFF)