lib/40480: With USE_FORT=yes in mk.conf libevent compile fails

[gabdelmalik%avdat.com.au@localhost]

>Number:         40480
>Category:       lib
>Synopsis:       With USE_FORT=yes in mk.conf libevent compile fails
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 26 09:15:00 +0000 2009
>Originator:     George Abdelmalik
>Release:        5.0_RC1
>Organization:
ADS
>Environment:
NetBSD bart.fork.id.au 4.99.73 NetBSD 4.99.73 (BART) #0: Thu Oct 23 22:40:26 
EST 2008  
srcmstr%bart.fork.id.au@localhost:/vstore/netbsd-current/obj/sys/arch/amd64/compile/BART
 amd64

>Description:
lib/libevent/evdns.c line 77 unconditionally  #defines _FORTIFY_SOURCE 3

when mk.conf contains:
  USE_FORT=       yes
The build terminates in error at that line citing redefinition of 
_FORTIFY_SOURCE

>How-To-Repeat:
Run build.sh with USE_FORT=yes specified in mk.conf.
>Fix:
Enclose affected line within #ifndef, such that it becomes;
#ifndef _FORTIFY_SOURCE
#define _FORTIFY_SOURCE 3
#endif