Add needed functions for acid to link.

src/platform/linux/mod.rs

@@ -219,8 +219,8 @@ impl Pal for Sys {
         e(unsafe { syscall!(FTRUNCATE, fildes, length) }) as c_int
     }
 
-    fn futex(addr: *mut c_int, op: c_int, val: c_int, val2: usize) -> c_int {
-        unsafe { syscall!(FUTEX, addr, op, val, val2, 0, 0) as c_int }
+    fn futex(addr: *mut c_int, op: c_int, val: c_int, val2: usize) -> Result<c_long, crate::pthread::Errno> {
+        e_raw(unsafe { syscall!(FUTEX, addr, op, val, val2, 0, 0)}).map(|r| r as c_long).map_err(|e| Errno(e as c_int))
     }
 
     fn futimens(fd: c_int, times: *const timespec) -> c_int {