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

libc/calls/thunks/fork-sysv.S

@@ -0,0 +1,41 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 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/dce.h"
+#include "libc/macros.h"
+
+/	Makes fork() kernel ABI consistent across UNIX systems.
+/
+/	@return	0 if parent, pid if child, or -1 on error
+fork$sysv:
+	push	%rbp
+	mov	%rsp,%rbp
+	.profilable
+	call	__fork$sysv
+#if SupportsXnu()
+	testb	IsXnu()
+	jz	1f
+	cmp	$-1,%rax
+	je	1f
+	neg	%edx			# edx is 0 for parent and 1 for child
+	not	%edx			# eax always returned with childs pid
+	and	%edx,%eax
+#endif
+1:	pop	%rbp
+	ret
+	.endfn	fork$sysv,globl,hidden

libc/calls/thunks/ftruncate-sysv.S

@@ -21,6 +21,6 @@
 
 /	Directly calls ftruncate() impl on host o/s if available.
 ftruncate$sysv:
-	mov	%rsp,%rdx			# openbsd:pad
+	mov	%rsi,%rdx			# openbsd:pad
 	jmp	__ftruncate$sysv
-	.endfn	ftruncate$sysv,globl
+	.endfn	ftruncate$sysv,globl,hidden

libc/calls/thunks/lseek-sysv.S

@@ -29,7 +29,7 @@ lseek$sysv:
 	cmovnz	.Lzero(%rip),%rsi
 #endif
 	jmp	__lseek$sysv
-	.endfn	lseek$sysv,globl
+	.endfn	lseek$sysv,globl,hidden
 
 	.rodata.cst8
 .Lzero:	.quad	0

libc/calls/thunks/mmap-sysv.S

@@ -27,4 +27,4 @@ mmap$sysv:
 	call	__mmap$sysv
 	leave
 	ret
-	.endfn	mmap$sysv,globl
+	.endfn	mmap$sysv,globl,hidden

libc/calls/thunks/onwincrash.S

@@ -23,4 +23,4 @@
 __wincrash$nt:
 	ezlea	__wincrash,ax
 	jmp	__nt2sysv
-	.endfn	__wincrash$nt,globl
+	.endfn	__wincrash$nt,globl,hidden

libc/calls/thunks/pread-sysv.S

@@ -23,4 +23,4 @@
 pread$sysv:
 	mov	%rcx,%r8			# openbsd:pad
 	jmp	__pread$sysv
-	.endfn	pread$sysv,globl
+	.endfn	pread$sysv,globl,hidden

libc/calls/thunks/preadv-sysv.S

@@ -23,4 +23,4 @@
 preadv$sysv:
 	mov	%rcx,%r8			# openbsd:pad
 	jmp	__preadv$sysv
-	.endfn	preadv$sysv,globl
+	.endfn	preadv$sysv,globl,hidden

libc/calls/thunks/pwrite-sysv.S

@@ -23,4 +23,4 @@
 pwrite$sysv:
 	mov	%rcx,%r8			# openbsd:pad
 	jmp	__pwrite$sysv
-	.endfn	pwrite$sysv,globl
+	.endfn	pwrite$sysv,globl,hidden

libc/calls/thunks/pwritev-sysv.S

@@ -23,4 +23,4 @@
 pwritev$sysv:
 	mov	%rcx,%r8			# openbsd:pad
 	jmp	__pwritev$sysv
-	.endfn	pwritev$sysv,globl
+	.endfn	pwritev$sysv,globl,hidden

libc/calls/thunks/truncate-sysv.S

@@ -21,6 +21,6 @@
 
 /	Directly calls truncate() impl on host o/s if available.
 truncate$sysv:
-	mov	%rsp,%rdx			# openbsd:pad
+	mov	%rsi,%rdx			# openbsd:pad
 	jmp	__truncate$sysv
-	.endfn	truncate$sysv,globl
+	.endfn	truncate$sysv,globl,hidden