FS-8055: [build] add confdir variable to freeswitch.pc

build/freeswitch.pc.in

@@ -7,6 +7,7 @@ modulesdir=@modulesdir@
 runtimedir=@runtimedir@
 logfiledir=@logfiledir@
 sysconfdir=@sysconfdir@
+confdir=@confdir@
 dbdir=@dbdir@
 htdocsdir=@htdocsdir@
 localstatedir=@localstatedir@