Fix XNU / FreeBSD / OpenBSD / RHEL5 / NT bugs

For the first time ever, all tests in this codebase now pass, when
run automatically on macos, freebsd, openbsd, rhel5, rhel7, alpine
and windows via the network using the runit and runitd build tools

- Fix vfork exec path etc.
- Add XNU opendir() support
- Add OpenBSD opendir() support
- Add Linux history to syscalls.sh
- Use copy_file_range on FreeBSD 13+
- Fix system calls with 7+ arguments
- Fix Windows with greater than 16 FDs
- Fix RUNIT.COM and RUNITD.COM flakiness
- Fix OpenBSD munmap() when files are mapped
- Fix long double so it's actually long on Windows
- Fix OpenBSD truncate() and ftruncate() thunk typo
- Let Windows fcntl() be used on socket files descriptors
- Fix Windows fstat() which had an accidental printf statement
- Fix RHEL5 CLOCK_MONOTONIC by not aliasing to CLOCK_MONOTONIC_RAW

This is wonderful. I never could have dreamed it would be possible
to get it working so well on so many platforms with tiny binaries.

Fixes #31
Fixes #25
Fixes #14

test/libc/calls/mkntcmdline_test.c

@@ -0,0 +1,85 @@
+/*-*- 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 2020 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/ntspawn.h"
+#include "libc/errno.h"
+#include "libc/mem/mem.h"
+#include "libc/runtime/gc.h"
+#include "libc/str/str.h"
+#include "libc/testlib/testlib.h"
+
+char16_t cmdline[ARG_MAX];
+
+TEST(mkntcmdline, emptyArgvList_isEmpty) {
+  char *argv[] = {NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"", cmdline);
+}
+
+TEST(mkntcmdline, emptyArg_getsQuoted) {
+  char *argv[] = {"", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"\"\"", cmdline);
+}
+
+TEST(mkntcmdline, ignoranceIsBliss) {
+  char *argv[] = {"echo", "hello", "world", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"echo hello world", cmdline);
+}
+
+TEST(mkntcmdline, spaceInArgument_getQuotesWrappedAround) {
+  char *argv[] = {"echo", "hello there", "world", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"echo \"hello there\" world", cmdline);
+}
+
+TEST(mkntcmdline, justQuote) {
+  char *argv[] = {"\"", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"\"\\\"\"", cmdline);
+}
+
+TEST(mkntcmdline, justSlash) {
+  char *argv[] = {"\\", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"\\", cmdline);
+}
+
+TEST(mkntcmdline, justSlashQuote) {
+  char *argv[] = {"\\\"", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"\"\\\\\\\"\"" /* "\\\"" */, cmdline);
+}
+
+TEST(mkntcmdline, basicQuoting) {
+  char *argv[] = {"a\"b c", "d", NULL};
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv));
+  EXPECT_STREQ(u"\"a\\\"b c\" d" /* "a\"b c" d */, cmdline);
+}
+
+TEST(mkntcmdline, testUnicode) {
+  char *argv1[] = {
+      strdup("(╯°□°)╯"),
+      strdup("要依法治国是赞美那些谁是公义的和惩罚恶人。 - 韩非"),
+      NULL,
+  };
+  EXPECT_NE(-1, mkntcmdline(cmdline, argv1));
+  EXPECT_STREQ(u"(╯°□°)╯ \"要依法治国是赞美那些谁是公义的和惩罚恶人。 - 韩非\"",
+               cmdline);
+}