Add sysb and sysc scaffolding.

Now that we have the Linux Kernel built, we move to a full-disk (rather
than initramfs) setup in sysc. However, we cannot assume the seed kernel
has support for mounting hard drives. So, first we need to kexec into
sysb, which is used as a jumping off point to create the hard drive for
sysc.

Additionally, since 2.6.16 does not have support for on-demand initramfs
(initramfs must be built into kernel), we will have to rebuild the linux
kernel within sysb without the initramfs.

All of this process is not performed for chroot mode. Instead, we skip
sysb and jump straight to sysc, copying over appropriate data.

The python scripts have been changed slightly. Each sys* inherits
SysGeneral, which contains various functions which are not specific to
any sys* and simplifies those files. rootfs now also handles sysb and
sysc.

bootstrap.cfg also gives an indication whether we are running in a
chroot to avoid attempting to kexec/mount within a chroot.

sysc/mpfr-4.1.0/checksums

@@ -0,0 +1,2 @@
+c37eb935fe06afa7467369ac16d83b39d55f83aa01a53e15f5b8b1595dce298f  /image/lib/musl/libmpfr.a
+225354a11b48c143c564393525ad1202d28ab40a83fb1a27964e731c2373c9de  /image/lib/musl/libmpfr.la

sysc/mpfr-4.1.0/files/mparam.h

@@ -0,0 +1,21 @@
+/*
+SPDX-FileCopyrightText: 2005-2020 Free Software Foundation, Inc.
+SPDX-License-Identifier: GPL-3.0-or-later
+*/
+
+/* This file is truncated version of src/mparam.h
+*/
+
+#ifndef __MPFR_IMPL_H__
+# error "MPFR Internal not included"
+#endif
+
+#define MPFR_TUNE_CASE "default"
+
+/****************************************************************
+ * Default values of Threshold.                                 *
+ * Must be included in any case: it checks, for every constant, *
+ * if it has been defined, and it sets it to a default value if *
+ * it was not previously defined.                               *
+ ****************************************************************/
+#include "generic/mparam.h"

sysc/mpfr-4.1.0/mpfr-4.1.0.sh

@@ -0,0 +1,28 @@
+# SPDX-FileCopyrightText: 2021 Andrius Štikonas <andrius@stikonas.eu>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+src_prepare() {
+    default
+
+    find . -name '*.info' -delete
+    autoreconf-2.69 -fi
+}
+
+src_configure() {
+    ./configure \
+        --prefix="${PREFIX}" \
+        --libdir="${PREFIX}/lib/musl" \
+        --disable-shared
+
+    # Disable tuning as that might cause non-reproducible build
+    mv mparam.h src
+}
+
+src_compile() {
+    make MAKEINFO=true DESTDIR="${DESTDIR}"
+}
+
+src_install() {
+    make MAKEINFO=true DESTDIR="${DESTDIR}" install
+}