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

examples/crashreport2.c

@@ -0,0 +1,52 @@
+#if 0
+/*─────────────────────────────────────────────────────────────────╗
+│ To the extent possible under law, Justine Tunney has waived      │
+│ all copyright and related or neighboring rights to this file,    │
+│ as it is written in the following disclaimers:                   │
+│   • http://unlicense.org/                                        │
+│   • http://creativecommons.org/publicdomain/zero/1.0/            │
+╚─────────────────────────────────────────────────────────────────*/
+#endif
+#include "libc/calls/calls.h"
+#include "libc/log/log.h"
+#include "libc/stdio/stdio.h"
+
+/**
+ * @fileoverview CTRL+\ debugging example
+ *
+ *     make -j8 -O o//examples/crashreport2.com
+ *     o//examples/crashreport2.com
+ *
+ * Assuming you call ShowCrashReports() from main(), you can press
+ * `CTRL+\` at anny time to generate a `SIGQUIT` message that lets you
+ * debug wrongness and freezups.
+ *
+ * On supported platforms, this will cause GDB to automatically attach.
+ * The nice thing about this, is you can start stepping through your
+ * code at the precice instruction where the interrupt happened. See
+ * `libc/log/attachdebugger.c` to see how it works.
+ *
+ * If you wish to suppress the auto-GDB behavior, then:
+ *
+ *     export GDB=
+ *
+ * Or alternatively:
+ *
+ *    extern int __isworker;
+ *    __isworker = true;
+ *
+ * Will cause your `SIGQUIT` handler to just print a crash report
+ * instead. This is useful for production software that might be running
+ * in a terminal environment like GNU Screen, but it's not desirable to
+ * have ten worker processes trying to attach GDB at once.
+ */
+
+int main(int argc, char *argv[]) {
+  volatile int64_t x;
+  ShowCrashReports();
+  printf("please press ctrl+\\ and see what happens...\n");
+  sigsuspend(0);
+  printf("\n\n");
+  printf("congratulations! your program is now resuming\n");
+  return 0;
+}