commit 090bf50771ec1e5d089b0ae0488059a5643883b2
Author: Raphael Kubo da Costa <rakuco@FreeBSD.org>
Date:   Sun Dec 27 01:24:34 2015 +0100

    forkfd: Only enable pipe2 on FreeBSD >= 10.0.

    The system call is not present on earlier releases, and since the 9.x
    series will be supported until the end of 2016, add a check for the
    __FreeBSD_version macro and only enable pipe2 support if the value is
    high enough.

    Change-Id: I5633531cec7e95d42ff5f4b14afe772ae8d7d66d
    Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

--- src/3rdparty/forkfd/forkfd.c
+++ src/3rdparty/forkfd/forkfd.c
@@ -62,7 +62,7 @@
 #  undef HAVE_WAITID
 #endif
 
-#if defined(__FreeBSD__)
+#if defined(__FreeBSD__) && defined(__FreeBSD_version) && __FreeBSD_version >= 1000032
 #  define HAVE_PIPE2    1
 #endif