https://github.com/kinetiknz/cubeb/commit/16f9ccc064f2

--- mozilla/media/libcubeb/src/cubeb_jack.cpp.orig	2017-07-07 05:37:16 UTC
+++ mozilla/media/libcubeb/src/cubeb_jack.cpp
@@ -8,7 +8,9 @@
  */
 #define _DEFAULT_SOURCE
 #define _BSD_SOURCE
+#ifndef __FreeBSD__
 #define _POSIX_SOURCE
+#endif
 #include <algorithm>
 #include <dlfcn.h>
 #include <limits>