add O_DIRECT flag (#527)

Author: jordanisaacs

src/backend/libc/fs/types.rs

@@ -259,6 +259,17 @@ bitflags! {
             target_os = "linux",
         ))]
         const NOATIME = c::O_NOATIME;
+
+        /// `O_DIRECT`
+        #[cfg(any(
+            target_os = "android",
+            target_os = "emscripten",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "netbsd",
+        ))]
+        const DIRECT = c::O_DIRECT;
     }
 }
 

src/backend/linux_raw/fs/types.rs

@@ -198,6 +198,9 @@ bitflags! {
 
         /// `O_NOATIME`
         const NOATIME = linux_raw_sys::general::O_NOATIME;
+
+        /// `O_DIRECT`
+        const DIRECT = linux_raw_sys::general::O_DIRECT;
     }
 }