freebsd adding CLOSE_RANGE_CLOEXEC flag

(backport <rust-lang#3996>)
(cherry picked from commit 0fb363c)

Author: devnexen

libc-test/semver/freebsd.txt

@@ -264,6 +264,7 @@ CLOCK_UPTIME
 CLOCK_UPTIME_FAST
 CLOCK_UPTIME_PRECISE
 CLOCK_VIRTUAL
+CLOSE_RANGE_CLOEXEC
 CMGROUP_MAX
 CMSG_DATA
 CMSG_FIRSTHDR

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -4968,6 +4968,10 @@ pub const TFD_CLOEXEC: ::c_int = O_CLOEXEC;
 pub const TFD_TIMER_ABSTIME: ::c_int = 0x01;
 pub const TFD_TIMER_CANCEL_ON_SET: ::c_int = 0x02;
 
+// sys/unistd.h
+
+pub const CLOSE_RANGE_CLOEXEC: ::c_uint = 1 << 2;
+
 cfg_if! {
     if #[cfg(libc_const_extern_fn)] {
         pub const fn MAP_ALIGNED(a: ::c_int) -> ::c_int {