Fix bugs and make improvements

- Get clone() working on FreeBSD
- Increase some Python build quotas
- Add more atomic builtins to chibicc
- Fix ASAN poisoning of alloca() memory
- Make MODE= mandatory link path tinier
- Improve the examples folder a little bit
- Start working on some more resource limits
- Make the linenoise auto-complete UI as good as GNU readline
- Update compile.com, avoiding AVX codegen on non-AVX systems
- Make sure empty path to syscalls like opendir raises ENOENT
- Correctly polyfill ENOENT vs. ENOTDIR on the New Technology
- Port bestline's paredit features to //third_party/linenoise
- Remove workarounds for RHEL 5.0 bugs that were fixed in 5.1

libc/calls/sigprocmask-sysv.c

@@ -0,0 +1,48 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/internal.h"
+
+int sys_sigprocmask(int how, const sigset_t *opt_set,
+                    sigset_t *opt_out_oldset) {
+  int res, rc, arg1;
+  sigset_t old = {0};
+  const sigset_t *arg2;
+  if (!IsOpenbsd()) {
+    rc = __sys_sigprocmask(how, opt_set, opt_out_oldset ? &old : 0, 8);
+  } else {
+    if (opt_set) {
+      // openbsd only supports 32 signals so it passses them in a reg
+      arg1 = how;
+      arg2 = (sigset_t *)(uintptr_t)(*(uint32_t *)opt_set);
+    } else {
+      arg1 = how;  // SIG_BLOCK
+      arg2 = 0;    // changes nothing
+    }
+    if ((res = __sys_sigprocmask(arg1, arg2, 0, 0)) != -1) {
+      memcpy(&old, &res, sizeof(res));
+      rc = 0;
+    } else {
+      rc = -1;
+    }
+  }
+  if (rc != -1 && opt_out_oldset) {
+    *opt_out_oldset = old;
+  }
+  return rc;
+}