[PATCH] erofs-utils: fix up Mac OS build again

[Gao Xiang]

Failed on Mac OS X 10.15.7 again.

Signed-off-by: Gao Xiang <xiang at kernel.org>
---
 include/erofs/internal.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index 7dc5ff006466..b939155ac951 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -34,7 +34,9 @@ typedef unsigned short umode_t;
 #error incompatible PAGE_SIZE is already defined
 #endif
 
+#ifndef PAGE_MASK
 #define PAGE_MASK		(~(PAGE_SIZE-1))
+#endif
 
 #define LOG_BLOCK_SIZE          (12)
 #define EROFS_BLKSIZ            (1U << LOG_BLOCK_SIZE)
-- 
2.20.1