install_prereq: Tweak flags when configuring pjproject.

This change does two things:
1. Disables debugging so assertions which can return an error do,
instead of asserting.
2. Enables IPv6 support.

ASTERISK-24632 #close
Reported by: Rusty Newton
........

Merged revisions 431843 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431844 65c4cc65-6c06-0410-ace0-fbb531ad65f3

contrib/scripts/install_prereq

@@ -163,7 +163,7 @@ install_unpackaged() {
 			cd pjproject
 			git pull
 		fi
-		./configure --enable-shared --with-external-speex --with-external-gsm --with-external-srtp --disable-sound --disable-resample && make && make install
+		./configure CFLAGS="-DNDEBUG -DPJ_HAS_IPV6=1" --enable-shared --with-external-speex --with-external-gsm --with-external-srtp --disable-sound --disable-resample && make && make install
 		cd ..
 		echo "/usr/local/lib" > /etc/ld.so.conf.d/usr_local.conf
 		/sbin/ldconfig