configure: include libimobiledevice CFLAGS in idevice_connection_get_fd check

AC_CHECK_DECL knows nothing about pkg-config shenanigans
see #183 (comment)

Author: artygus

configure.ac

@@ -52,7 +52,11 @@ AC_TYPE_UINT8_T
 AC_FUNC_MALLOC
 AC_FUNC_REALLOC
 AC_CHECK_FUNCS([memmove memset regcomp select socket stpcpy strcasecmp strncasecmp strchr strdup strndup strrchr strstr strtol])
+
+SAVE_CFLAGS=$CFLAGS
+CFLAGS="$CFLAGS $libimobiledevice_CFLAGS"
 AC_CHECK_DECL(idevice_connection_get_fd, [AC_DEFINE([HAVE_IDEVICE_CONNECTION_GET_FD], 1, [ ])], [], [#include <libimobiledevice/libimobiledevice.h>])
+CFLAGS=$SAVE_CFLAGS
 
 AC_CONFIG_FILES([Makefile src/Makefile include/Makefile examples/Makefile])