[libc] 优化fcntl.h定义

components/libc/compilers/common/fcntl.h

@@ -12,13 +12,10 @@
 
 #include <sys/types.h>
 
-#if defined(_WIN32)
-#define O_ACCMODE   (_O_RDONLY | _O_WRONLY | _O_RDWR)
-#endif
-
-#define O_RDONLY         00
-#define O_WRONLY         01
-#define O_RDWR           02
+#define O_RDONLY    0x0000      /* open for reading only */
+#define O_WRONLY    0x0001      /* open for writing only */
+#define O_RDWR      0x0002      /* open for reading and writing */
+#define O_ACCMODE   0x0003      /* mask for above modes */
 
 #define O_CREAT        0100
 #define O_EXCL         0200
@@ -43,8 +40,6 @@
 #define O_SEARCH  O_PATH
 #define O_EXEC    O_PATH
 
-#define O_ACCMODE (03|O_SEARCH)
-
 #define F_DUPFD  0
 #define F_GETFD  1
 #define F_SETFD  2