basic: fix build on architectures with small long

The x32 architecture has a small "long" type which is not enough to hold
struct statfs.f_type.

src/basic/stat-util.h

@@ -52,9 +52,8 @@ int path_is_os_tree(const char *path);
 int files_same(const char *filea, const char *fileb);
 
 /* The .f_type field of struct statfs is really weird defined on
- * different archs. Let's use our own type we know is sufficiently
- * larger to store the possible values. */
-typedef long statfs_f_type_t;
+ * different archs. Let's give its type a name. */
+typedef typeof(((struct statfs*)NULL)->f_type) statfs_f_type_t;
 
 bool is_fs_type(const struct statfs *s, statfs_f_type_t magic_value) _pure_;
 int fd_check_fstype(int fd, statfs_f_type_t magic_value);