Haiku: there is no setpriority on this platform.

src/bootstrap/lib.rs

@@ -177,7 +177,7 @@
 #[cfg(windows)]
 mod job;
 
-#[cfg(unix)]
+#[cfg(all(unix, not(target_os = "haiku")))]
 mod job {
     use libc;
 
@@ -188,7 +188,7 @@ pub unsafe fn setup(build: &mut ::Build) {
     }
 }
 
-#[cfg(not(any(unix, windows)))]
+#[cfg(any(target_os = "haiku", not(any(unix, windows))))]
 mod job {
     pub unsafe fn setup(_build: &mut ::Build) {
     }