Implemented getattr and source_stat.

Now filesystem implements getattr through source_stat,
which is a wrapper for an fstatat with
`dirfd == handle.root_path`.

sources/sourcefs.c

@@ -1,8 +1,9 @@
 #define _GNU_SOURCE
 
 #include "sourcefs.h"
-
 #include <fcntl.h>
+#include <stdio.h>
+#include <sys/stat.h>
 
 static struct source_files_handle {
   int root_fd;
@@ -19,3 +20,9 @@ int source_init(const char *root_path) {
 
   return 0;
 }
+
+// Currently this literally is a fstatat wrapper.
+int source_stat(const char *restrict pathname, struct stat *restrict statbuf) {
+  int statret = fstatat(handle.root_fd, pathname, statbuf, 0);
+  return statret;
+}