`.wraplock` broken again on read-only source directories

[mintsuki]

Describe the bug
Similar to #14948, it seems like the bug has come back on meson 1.10.0 (not sure if the first version with the issue back, but it's certainly a version with the issue)

To Reproduce
Attempt to perform an out-of-tree build with a read-only source directory.

Expected behavior
Meson should work, but it does not, and it fails with this trace:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/mesonbuild/mesonmain.py", line 193, in run
    return options.run_func(options)
           ~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/msetup.py", line 404, in run
    app.generate()
    ~~~~~~~~~~~~^^
  File "/usr/lib/python3/dist-packages/mesonbuild/msetup.py", line 196, in generate
    return self._generate(env, capture, vslite_ctx)
           ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/msetup.py", line 255, in _generate
    intr.run()
    ~~~~~~~~^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreter/interpreter.py", line 3063, in run
    super().run()
    ~~~~~~~~~~~^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 178, in run
    self.evaluate_codeblock(self.ast, start=1)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 203, in evaluate_codeblock
    raise e
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 195, in evaluate_codeblock
    self.evaluate_statement(cur)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 209, in evaluate_statement
    return self.function_call(cur)
           ~~~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 524, in function_call
    (h_posargs, h_kwargs) = self.reduce_arguments(node.args)
                            ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 609, in reduce_arguments
    reduced_val = self.evaluate_statement(val)
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 233, in evaluate_statement
    return self.evaluate_arraystatement(cur)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 267, in evaluate_arraystatement
    (arguments, kwargs) = self.reduce_arguments(cur.args)
                          ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 602, in reduce_arguments
    reduced_pos = [self.evaluate_statement(arg) for arg in args.arguments]
                   ~~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 215, in evaluate_statement
    return self.method_call(cur)
           ~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 550, in method_call
    obj = self.evaluate_statement(invocable)
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 209, in evaluate_statement
    return self.function_call(cur)
           ~~~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/interpreterbase.py", line 536, in function_call
    res = func(node, func_args, kwargs)
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/decorators.py", line 237, in wrapper
    return f(*nargs, **wrapped_kwargs)
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreterbase/decorators.py", line 565, in wrapper
    return f(*wrapped_args, **wrapped_kwargs)
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreter/interpreter.py", line 857, in func_subproject
    return self.do_subproject(args[0], kw)
           ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/interpreter/interpreter.py", line 915, in do_subproject
    subdir, method = r.resolve(subp_name, force_method)
                     ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/wrap/wrap.py", line 610, in resolve
    with DirectoryLock(self.subdir_root, '.wraplock',
         ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                       DirectoryLockAction.WAIT,
                       ^^^^^^^^^^^^^^^^^^^^^^^^^
                       'Failed to lock subprojects directory', optional=True):
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/mesonbuild/utils/platform.py", line 111, in __exit__
    if self.lockfile is None or self.lockfile.closed:
       ^^^^^^^^^^^^^
AttributeError: 'DirectoryLock' object has no attribute 'lockfile'

../../../base_dir/sources/gcon/meson.build:19:8: ERROR: Unhandled python exception

    This is a Meson bug and should be reported!

I would suggest adding a test to avoid breaking this in the future.

[bonzini]

Introduced by ab7684d (utils/platform: Use a type declaration instead of default value, it really wanted a default value);

[thesamesam]

#15430