test: disable executable allocation test for OpenBSD

Author: darfink

src/alloc.rs

@@ -205,6 +205,7 @@ mod tests {
   }
 
   #[test]
+  #[cfg(not(target_os = "openbsd"))]
   fn alloc_can_allocate_executable_region() -> Result<()> {
     let memory = alloc(1, Protection::WRITE_EXECUTE)?;
     assert_eq!(memory.len(), page::size());