Remove the notion of "sys*"

- This idea originates from very early in the project and was, at the
  time, a very easy way to categorise things.
- Now, it doesn't really make much sense - it is fairly arbitary, often
  occuring when there is a change in kernel, but not from builder-hex0
  to fiwix, and sysb is in reality completely unnecessary.
- In short, the sys* stuff is a bit of a mess that makes the project
  more difficult to understand.
- This puts everything down into one folder and has a manifest file that
  is used to generate the build scripts on the fly rather than using
  coded scripts.
- This is created in the "seed" stage.

stage0-posix -- (calls) --> seed -- (generates) --> main steps

Alongside this change there are a variety of other smaller fixups to the
general structure of the live-bootstrap rootfs.

- Creating a rootfs has become much simpler and is defined as code in
  go.sh. The new structure, for an about-to-be booted system, is

/
-- /steps (direct copy of steps/)
-- /distfiles (direct copy of distfiles/)
-- all files from seed/*
-- all files from seed/stage0-posix/*

- There is no longer such a thing as /usr/include/musl, this didn't
  really make any sense, as musl is the final libc used. Rather, to
  separate musl and mes, we have /usr/include/mes, which is much easier
  to work with.
- This also makes mes easier to blow away later.
- A few things that weren't properly in packages have been changed;
  checksum-transcriber, simple-patch, kexec-fiwix have all been given
  fully qualified package names.
- Highly breaking change, scripts now exist in their package directory
  but NOT WITH THE packagename.sh. Rather, they use pass1.sh, pass2.sh,
  etc. This avoids manual definition of passes.
  - Ditto with patches; default directory is patches, but then any patch
    series specific to a pass are named patches-passX.

steps/musl-1.1.24/patches/set_thread_area.patch

@@ -0,0 +1,35 @@
+SPDX-FileCopyrightText: 2020 Rich Felker <dalias@aerifal.cx>
+
+SPDX-License-Identifier: MIT
+
+From 0b0640219338b80cf47026d1970b5503414ed7f3 Mon Sep 17 00:00:00 2001
+From: Rich Felker <dalias@aerifal.cx>
+Date: Sun, 30 Aug 2020 21:37:12 -0400
+Subject: fix i386 __set_thread_area fallback
+
+this code is only needed for pre-2.6 kernels, which are not actually
+supported anyway, and was never tested. the fallback path using
+SYS_modify_ldt failed to clear the upper bits of %eax (all ones due to
+SYS_set_thread_area's return value being an error) before modifying
+%al to attempt a new syscall.
+---
+ src/thread/i386/__set_thread_area.s | 1 +
+ 1 file changed, 1 insertion(+)
+
+(limited to 'src/thread/i386/__set_thread_area.s')
+
+diff --git src/thread/i386/__set_thread_area.s src/thread/i386/__set_thread_area.s
+index c2c21dd5..aa6852be 100644
+--- src/thread/i386/__set_thread_area.s
++++ src/thread/i386/__set_thread_area.s
+@@ -28,6 +28,7 @@ __set_thread_area:
+ 	ret
+ 2:
+ 	mov %ebx,%ecx
++	xor %eax,%eax
+ 	xor %ebx,%ebx
+ 	xor %edx,%edx
+ 	mov %ebx,(%esp)
+-- 
+cgit v1.2.1
+