Fix build and tests issues on OpenBSD 6.4+

1)  lutimes doesn't exist on OpenBSD so it needs to be under conditional
    compilation.

    The only "reference" that I could find related to this is the discussion
    here: https://github.com/rust-lang/libc/pull/790 .

2)  fexecve doesn't exist on OpenBSD so add conditional compilation for it
    in unistd and in related tests.

    The only "reference" that I could find is a mention that fexecve is
    not implemented on OpenBSD in the manual pages for signal(3) and
    sigaction(2):

    Official repository (search for "fexecve"):
    https://cvsweb.openbsd.org/src/lib/libc/sys/sigaction.2?rev=1.75&content-type=text/x-cvsweb-markup

    Github mirror:
    https://github.com/openbsd/src/blob/master/lib/libc/sys/sigaction.2#L619

3)  AIO doesn't work on OpenBSD so put test_aio_drop under conditional
    compilation.

4)  Add relevant changelog entries.

P.S. On OpenBSD remains the issue of test_scm_rights which builds
correctly but fails at runtime.

6 files changed, 48 insertions, 15 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fda5b690..a49686a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,11 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 ### Fixed
+- `lutimes` never worked on OpenBSD as it is not implemented on OpenBSD. It has
+  been removed. ([#1000](https://github.com/nix-rust/nix/pull/1000))
+- `fexecve` never worked on NetBSD or on OpenBSD as it is not implemented on
+  either OS. It has been removed. ([#1000](https://github.com/nix-rust/nix/pull/1000))
+
 ### Removed
 
 ## [0.12.0] 2018-11-28
diff --git a/src/sys/stat.rs b/src/sys/stat.rs
index e0367859..1e0936ed 100644
--- a/src/sys/stat.rs
+++ b/src/sys/stat.rs
@@ -209,7 +209,12 @@ pub fn utimes<P: ?Sized + NixPath>(path: &P, atime: &TimeVal, mtime: &TimeVal) -
 /// # References
 ///
 /// [lutimes(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/lutimes.html).
-#[cfg(not(target_os = "android"))]
+#[cfg(any(target_os = "linux",
+          target_os = "haiku",
+          target_os = "ios",
+          target_os = "macos",
+          target_os = "freebsd",
+          target_os = "netbsd"))]
 pub fn lutimes<P: ?Sized + NixPath>(path: &P, atime: &TimeVal, mtime: &TimeVal) -> Result<()> {
     let times: [libc::timeval; 2] = [*atime.as_ref(), *mtime.as_ref()];
     let res = path.with_nix_path(|cstr| unsafe {
diff --git a/src/unistd.rs b/src/unistd.rs
index 2c00f7f0..a41c1392 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -760,11 +760,12 @@ pub fn execvpe(filename: &CString, args: &[CString], env: &[CString]) -> Result<
 ///
 /// This function is similar to `execve`, except that the program to be executed
 /// is referenced as a file descriptor instead of a path.
+// Note for NetBSD and OpenBSD: although rust-lang/libc includes it (under
+// unix/bsd/netbsdlike/) fexecve is not currently implemented on NetBSD nor on
+// OpenBSD.
 #[cfg(any(target_os = "android",
-          target_os = "freebsd",
           target_os = "linux",
-          target_os = "netbsd",
-          target_os = "openbsd"))]
+          target_os = "freebsd"))]
 #[inline]
 pub fn fexecve(fd: RawFd, args: &[CString], env: &[CString]) -> Result<Void> {
     let args_p = to_exec_array(args);
diff --git a/test/sys/test_aio_drop.rs b/test/sys/test_aio_drop.rs
index 1f4a3e79..492da401 100644
--- a/test/sys/test_aio_drop.rs
+++ b/test/sys/test_aio_drop.rs
@@ -1,18 +1,23 @@
 extern crate nix;
 extern crate tempfile;
 
-use nix::sys::aio::*;
-use nix::sys::signal::*;
-use std::os::unix::io::AsRawFd;
-use tempfile::tempfile;
-
 // Test dropping an AioCb that hasn't yet finished.
 // This must happen in its own process, because on OSX this test seems to hose
 // the AIO subsystem and causes subsequent tests to fail
 #[test]
 #[should_panic(expected = "Dropped an in-progress AioCb")]
-#[cfg(not(target_env = "musl"))]
+#[cfg(all(not(target_env = "musl"),
+          any(target_os = "linux",
+              target_os = "ios",
+              target_os = "macos",
+              target_os = "freebsd",
+              target_os = "netbsd")))]
 fn test_drop() {
+    use nix::sys::aio::*;
+    use nix::sys::signal::*;
+    use std::os::unix::io::AsRawFd;
+    use tempfile::tempfile;
+
     const WBUF: &[u8] = b"CDEF";
 
     let f = tempfile().unwrap();
diff --git a/test/test_stat.rs b/test/test_stat.rs
index 9d27ce79..fae8df82 100644
--- a/test/test_stat.rs
+++ b/test/test_stat.rs
@@ -7,7 +7,14 @@ use std::time::{Duration, UNIX_EPOCH};
 use libc::{S_IFMT, S_IFLNK};
 
 use nix::fcntl;
-use nix::sys::stat::{self, fchmod, fchmodat, futimens, lutimes, stat, utimes, utimensat};
+use nix::sys::stat::{self, fchmod, fchmodat, futimens, stat, utimes, utimensat};
+#[cfg(any(target_os = "linux",
+          target_os = "haiku",
+          target_os = "ios",
+          target_os = "macos",
+          target_os = "freebsd",
+          target_os = "netbsd"))]
+use nix::sys::stat::lutimes;
 use nix::sys::stat::{Mode, FchmodatFlags, UtimensatFlags};
 
 #[cfg(not(any(target_os = "netbsd")))]
@@ -196,6 +203,12 @@ fn test_utimes() {
 }
 
 #[test]
+#[cfg(any(target_os = "linux",
+          target_os = "haiku",
+          target_os = "ios",
+          target_os = "macos",
+          target_os = "freebsd",
+          target_os = "netbsd"))]
 fn test_lutimes() {
     let tempdir = tempfile::tempdir().unwrap();
     let target = tempdir.path().join("target");
diff --git a/test/test_unistd.rs b/test/test_unistd.rs
index ead4b487..3fb50535 100644
--- a/test/test_unistd.rs
+++ b/test/test_unistd.rs
@@ -230,16 +230,20 @@ cfg_if!{
         execve_test_factory!(test_execve, execve, &CString::new("/system/bin/sh").unwrap());
         execve_test_factory!(test_fexecve, fexecve, File::open("/system/bin/sh").unwrap().into_raw_fd());
     } else if #[cfg(any(target_os = "freebsd",
-                        target_os = "linux",
-                        target_os = "openbsd"))] {
+                        target_os = "linux"))] {
         execve_test_factory!(test_execve, execve, &CString::new("/bin/sh").unwrap());
         execve_test_factory!(test_fexecve, fexecve, File::open("/bin/sh").unwrap().into_raw_fd());
     } else if #[cfg(any(target_os = "dragonfly",
                         target_os = "ios",
                         target_os = "macos",
-                        target_os = "netbsd"))] {
+                        target_os = "netbsd",
+                        target_os = "openbsd"))] {
         execve_test_factory!(test_execve, execve, &CString::new("/bin/sh").unwrap());
-        // No fexecve() on DragonFly, ios, macos, and NetBSD.
+        // No fexecve() on DragonFly, ios, macos, NetBSD, OpenBSD.
+        //
+        // Note for NetBSD and OpenBSD: although rust-lang/libc includes it
+        // (under unix/bsd/netbsdlike/) fexecve is not currently implemented on
+        // NetBSD nor on OpenBSD.
     }
 }