Fix Mac build.

Bug: 21669400
Change-Id: I961699b5559f75f782d048fdafbbb40c16457f88
diff --git a/Android.mk b/Android.mk
index ab79031..7a46ede 100644
--- a/Android.mk
+++ b/Android.mk
@@ -35,6 +35,10 @@
 
 LOCAL_CPP_EXTENSION := .cc
 
+ifeq ($(HOST_OS),darwin)
+LOCAL_CFLAGS := -D_FILE_OFFSET_BITS=64 -Doff64_t=off_t
+endif
+
 LOCAL_C_INCLUDES := $(LOCAL_PATH) external/e2fsprogs/lib
 LOCAL_SRC_FILES := $(sgdisk_src_files)