alacritty: add support for OpenBSD.

This commit expands the conditional compilation directives to support
building Alacritty for OpenBSD.  The build succeeds, and Alacritty runs
without issue once https://github.com/rust-lang/libc/pull/957 has been
merged and added to a versioned libc release.

This has been tested on the recently-released OpenBSD 6.3 on amd64 with
rustc 1.24.0 from its standard ports tree.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/tty.rs b/src/tty.rs
index 21c9659d..166a788e 100644
--- a/src/tty.rs
+++ b/src/tty.rs
@@ -87,7 +87,7 @@ fn openpty(rows: u8, cols: u8) -> (c_int, c_int) {
     (master, slave)
 }
 
-#[cfg(any(target_os = "macos",target_os = "freebsd"))]
+#[cfg(any(target_os = "macos",target_os = "freebsd",target_os = "openbsd"))]
 fn openpty(rows: u8, cols: u8) -> (c_int, c_int) {
     let mut master: c_int = 0;
     let mut slave: c_int = 0;