RFC: Disable clone3 for glibc 2.34

[Florian Weimer]

Reportedly, the docker package in Ubuntu as used by Github Actions and
others does not provide a way to enable the clone3 system call.  It
always fails with EPERM.

Should we apply a patch like this for the release?

diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c
index 1e7a8f6b35..4046c81180 100644
--- a/sysdeps/unix/sysv/linux/clone-internal.c
+++ b/sysdeps/unix/sysv/linux/clone-internal.c
@@ -48,17 +48,6 @@ __clone_internal (struct clone_args *cl_args,
 		  int (*func) (void *arg), void *arg)
 {
   int ret;
-#ifdef HAVE_CLONE3_WAPPER
-  /* Try clone3 first.  */
-  int saved_errno = errno;
-  ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
-  if (ret != -1 || errno != ENOSYS)
-    return ret;
-
-  /* NB: Restore errno since errno may be checked against non-zero
-     return value.  */
-  __set_errno (saved_errno);
-#endif
 
   /* Map clone3 arguments to clone arguments.  NB: No need to check
      invalid clone3 specific bits in flags nor exit_signal since this

My concern with this is that we don't know yet where the CET kernel API
will land exactly and if CET will require clone3.  So clone3 might have
to come back once we turn on CET, which is hopefully soon.

Thanks,
Florian