pkg/51515: www/firefox fails to build with webrtc option enabled

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>Number:         51515
>Category:       pkg
>Synopsis:       www/firefox fails to build with webrtc option enabled
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Sep 28 11:35:00 +0000 2016
>Originator:     Sevan Janiyan
>Release:        pkgsrc-current
>Organization:
>Environment:
NetBSD 7.0.1_PATCH (GENERIC) #0: Tue Sep 27 10:04:38 BST 2016 GENERIC i386
>Description:
Attempting to build www/firefox with the webrtc option enabled on NetBSD/7.0.1 i386, it fails due to lack of support for the SCTP implementation in NetBSD.

/usr/pkgsrc/www/firefox/work/build/_virtualenv/bin/python /usr/pkgsrc/www/firefox/work/firefox-49.0/config/expandlibs_gen.py -o libtoolkit_profile.a.desc Unified_cpp_toolkit_profile0.o  
/usr/pkgsrc/www/firefox/work/firefox-49.0/netwerk/sctp/src/netinet6/sctp6_usrreq.c: In function 'sctp6_notify':
/usr/pkgsrc/www/firefox/work/firefox-49.0/netwerk/sctp/src/netinet6/sctp6_usrreq.c:475:35: error: 'ICMP_UNREACH_ADMIN_PROHIBIT' undeclared (first use in this function)
             (icmph->icmp6_code == ICMP_UNREACH_ADMIN_PROHIBIT)) {
                                   ^
/usr/pkgsrc/www/firefox/work/firefox-49.0/netwerk/sctp/src/netinet6/sctp6_usrreq.c:475:35: note: each undeclared identifier is reported only once for each function it appears in
/usr/pkgsrc/www/firefox/work/firefox-49.0/config/rules.mk:891: recipe for target 'sctp6_usrreq.o' failed

>How-To-Repeat:
build www/firefox with PKG_OPTIONS.firefox=webrtc defined in mk.conf
>Fix: