This patch unbreaks the current build after tor!369 landed.

See: https://bugs.torproject.org/tpo/core/tor/40371

This change permits the newfstatat() system call, and fixes issues
40382 (and 40381).

This isn't a free change.  From the commit:

    // Libc 2.33 uses this syscall to implement both fstat() and stat().
    //
    // The trouble is that to implement fstat(fd, &st), it calls:
    //     newfstatat(fs, "", &st, AT_EMPTY_PATH)
    // We can't detect this usage in particular, because "" is a pointer
    // we don't control.  And we can't just look for AT_EMPTY_PATH, since
    // AT_EMPTY_PATH only has effect when the path string is empty.
    //
    // So our only solution seems to be allowing all fstatat calls, which
    // means that an attacker can stat() anything on the filesystem. That's
    // not a great solution, but I can't find a better one.

As of GCC 11.1.1, the compiler warns us about code like this:

     if (a)
         b;
         c;

and that's a good thing: we wouldn't want to "goto fail".  But we
had an instance if this in circuituse.c, which was making our
compilation sad.

Fixes bug 40380; bugfix on 0.3.0.1-alpha.

"ours" merge to avoid version bump.

"ours" to avoid version bump.

Welcome back ONION_V2_HOSTNAME! :)

Turns out that passing client authorization keys to ADD_ONION for v3 was
not working because we were not setting the "is_client_auth_enabled"
flag to true once the clients were configured. This lead to the
descriptor being encoded without the clients.

This patch removes that flag and instead adds an inline function that
can be used to check if a given service has client authorization
enabled.

This will be much less error prone of needing to keep in sync the client
list and a flag instead.

Fixes #40378

Signed-off-by: David Goulet <dgoulet@torproject.org>

Signed-off-by: David Goulet <dgoulet@torproject.org>

Conflicts:
  src/test/test.c

  Minor comment issue.

Fixes #40356

Signed-off-by: David Goulet <dgoulet@torproject.org>