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.

download-distfiles.sh

@@ -20,27 +20,18 @@ download_source() {
     echo "${checksum}  ${dest_path}" | sha256sum -c
 }
 
-download_for_sys() {
-    local sysdir="${1}"
-    local distfiles="${sysdir}/distfiles"
-
-    mkdir -p "${distfiles}"
-
-    local entry
-    for entry in "${sysdir}"/*; do
-        [ -e "${entry}/sources" ] || continue
-
-        local line
-        # shellcheck disable=SC2162
-        while read line; do
-            # This is intentional - we want to split out ${line} into separate arguments.
-            # shellcheck disable=SC2086
-            download_source "${distfiles}" ${line}
-        done < "${entry}/sources"
-    done
-}
-
 set -e
+
 cd "$(dirname "$(readlink -f "$0")")"
-download_for_sys sysa
-download_for_sys sysc
+mkdir -p distfiles
+
+for entry in steps/*; do
+    [ -e "${entry}/sources" ] || continue
+
+    # shellcheck disable=SC2162
+    while read line; do
+        # This is intentional - we want to split out ${line} into separate arguments.
+        # shellcheck disable=SC2086
+        download_source distfiles ${line}
+    done < "${entry}/sources"
+done