builtin/meta_oils.py: Mark internal files as persistent

This fixes the following issue:

    $ cat source.osh
    exec 25>out
    echo hello>&25
    cat out
    $ bin/osh -c '. ./source.osh'
    hello
    [ -c flag ]:1: . builtin I/O error: Bad file descriptor

Signed-off-by: Andrii Sultanov <[email protected]>

Author: last-genius

builtin/meta_oils.py

@@ -198,7 +198,7 @@ def _LoadDiskFile(self, fs_path, blame_loc):
         # type: (str, loc_t) -> Tuple[mylib.LineReader, cmd_parse.CommandParser]
         try:
             # Shell can't use descriptors 3-9
-            f = self.fd_state.Open(fs_path)
+            f = self.fd_state.Open(fs_path, persistent=True)
         except (IOError, OSError) as e:
             self.errfmt.Print_(
                 '%s %r failed: %s' %
@@ -207,6 +207,7 @@ def _LoadDiskFile(self, fs_path, blame_loc):
             return None, None
 
         line_reader = reader.FileLineReader(f, self.arena)
+        self.fd_state.SetCallback(f, line_reader.ReplaceFd)
         c_parser = self.parse_ctx.MakeOshParser(line_reader)
         return f, c_parser