Fix some issues with the OSX port

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/compiler/compiler.h b/compiler/compiler.h
index 0a08bb1..c1923dd 100644
--- a/compiler/compiler.h
+++ b/compiler/compiler.h
@@ -15,6 +15,8 @@
 
 #define uninitialized_var(x) x = x
 
+#ifndef __weak
 #define __weak	__attribute__((weak))
+#endif
 
 #endif