tools/nolibc: check for S_I* macros before defining them

Defining S_I* flags in types.h can cause some build failures if
linux/stat.h is included prior to it. But if not defined, some toolchains
that include some glibc parts will in turn fail because linux/stat.h
already takes care of avoiding these definitions when glibc is present.

Let's preserve the macros here but first include linux/stat.h and check
for their definition before doing so. We also define the previously
missing permission macros so that we don't get a different behavior
depending on the first include found.

Cc: Feiyang Chen <chenfeiyang@loongson.cn>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/types.h

@@ -9,6 +9,7 @@
 
 #include "std.h"
 #include <linux/time.h>
+#include <linux/stat.h>
 
 
 /* Only the generic macros and types may be defined here. The arch-specific
@@ -16,7 +17,11 @@
  * the layout of sys_stat_struct must not be defined here.
  */
 
-/* stat flags (WARNING, octal here) */
+/* stat flags (WARNING, octal here). We need to check for an existing
+ * definition because linux/stat.h may omit to define those if it finds
+ * that any glibc header was already included.
+ */
+#if !defined(S_IFMT)
 #define S_IFDIR        0040000
 #define S_IFCHR        0020000
 #define S_IFBLK        0060000
@@ -34,6 +39,22 @@
 #define S_ISLNK(mode)  (((mode) & S_IFMT) == S_IFLNK)
 #define S_ISSOCK(mode) (((mode) & S_IFMT) == S_IFSOCK)
 
+#define S_IRWXU 00700
+#define S_IRUSR 00400
+#define S_IWUSR 00200
+#define S_IXUSR 00100
+
+#define S_IRWXG 00070
+#define S_IRGRP 00040
+#define S_IWGRP 00020
+#define S_IXGRP 00010
+
+#define S_IRWXO 00007
+#define S_IROTH 00004
+#define S_IWOTH 00002
+#define S_IXOTH 00001
+#endif
+
 /* dirent types */
 #define DT_UNKNOWN     0x0
 #define DT_FIFO        0x1