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

test/libc/calls/unlinkat_test.c

@@ -17,11 +17,29 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/dce.h"
 #include "libc/sysv/consts/at.h"
 #include "libc/testlib/testlib.h"
 
 char testlib_enable_tmp_setup_teardown;
 
+TEST(unlink, efault) {
+  ASSERT_SYS(EFAULT, -1, unlink(0));
+  if (IsWindows() && !IsAsan()) return;  // not possible
+  ASSERT_SYS(EFAULT, -1, unlink((void *)77));
+}
+
+TEST(unlink, enoent) {
+  ASSERT_SYS(ENOENT, -1, unlink(""));
+  ASSERT_SYS(ENOENT, -1, unlink("doesnotexist"));
+  ASSERT_SYS(ENOENT, -1, unlink("o/doesnotexist"));
+}
+
+TEST(unlink, enotdir) {
+  ASSERT_SYS(0, 0, touch("o", 0644));
+  ASSERT_SYS(ENOTDIR, -1, unlink("o/doesnotexist"));
+}
+
 TEST(unlinkat, test) {
   int i, fd;
   EXPECT_EQ(0, touch("mytmp", 0644));