export variable CONFFLAGS

[rennes]

Hello,
I am trying to export the variable 'CONFFLAGS' for 'apr' package on 
GNU/Hurd as follows:

(arguments
     #:make-flags ("CONFFLAGS+=apr_cv_struct_ipmreq=no"
                        (string-append "PREFIX=" %output))


This way does not work!, the Debian project does it as follows:

ifeq (hurd,$(DEB_HOST_ARCH_OS))
  CONFFLAGS += apr_cv_struct_ipmreq=no
endif

This due to the Hurd does not support multicast yet.

Thanks