tools/libfsimage: Fix PATH_MAX redefinition error

If PATH_MAX is already defined in the system (e.g. in /usr/include/limits.h
header) then gcc will trigger a redefinition error because of -Werror.

Signed-off-by: Costin Lupu <costin.lupu@cs.pub.ro>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Acked-by: Ian Jackson <iwj@xenproject.org>

tools/libfsimage/ext2fs/fsys_ext2fs.c

@@ -278,7 +278,9 @@ struct ext4_extent_header {
 
 #define EXT2_SUPER_MAGIC      0xEF53	/* include/linux/ext2_fs.h */
 #define EXT2_ROOT_INO              2	/* include/linux/ext2_fs.h */
+#ifndef PATH_MAX
 #define PATH_MAX                1024	/* include/linux/limits.h */
+#endif
 #define MAX_LINK_COUNT             5	/* number of symbolic links to follow */
 
 /* made up, these are pointers into FSYS_BUF */

tools/libfsimage/reiserfs/fsys_reiserfs.c

@@ -284,7 +284,9 @@ struct reiserfs_de_head
 #define S_ISDIR(mode) (((mode) & 0170000) == 0040000)
 #define S_ISLNK(mode) (((mode) & 0170000) == 0120000)
 
+#ifndef PATH_MAX
 #define PATH_MAX       1024	/* include/linux/limits.h */
+#endif
 #define MAX_LINK_COUNT    5	/* number of symbolic links to follow */
 
 /* The size of the node cache */