Complete the kernel bootstrap by adding kexec of Linux from Fiwix.

A tiny bootloader bootstrap has been added to compile the builder-hex0 kernel from hex0 source.
The boot compiler is builder-hex0-x86-stage1.hex0 and builder-hex0-x86-stage1.bin.
The builder-hex0 kernel is now named builder-hex0-x86-stage2.hex0.
The inclusion of a binary seed resolves the problem with the previous strategy which used an
architecture-specific hex0 compiler.

If sysb detects a full disk (i.e. DISK=sda) it now partitions the disk unconditionally because
previously fdisk was reporting existing but empty partitions which resulted in no
parititions being created.

e2fsprogs is now built with --disable-tls because musl was built on Fiwix without full threading
support and mkfs.ext4 was crashing without disabling thread local storage.

kexec-linux writes the linux kernel and initramfs to a RAM drive on Fiwix which ensure
a pre-allocated contiguous memory block. The following is written to the ram drive:
a 32-bit number which is the size of the kernel in bytes, a 32-bit number which is the size
of the initramfs in bytes, followed by the Linux kernel image, followed by the initramfs.

kexec-fiwix invokes a sync syscall to ensure all writes are flushed to
the ram drive and then initiates the kexec by shutting down Fiwix with a reboot syscall.
Fiwix knows whether and how to perform the kexec based on kernel parameters passed to it.

sysa/run2.sh

@@ -25,16 +25,20 @@ create_sysb() {
 }
 
 go_sysb() {
-    # Mount proc for kexec
-    mkdir /proc /etc
-    mount -t proc proc /proc
-    # kexec time
-    echo "Loading kernel + sysb initramfs using kexec"
-    kexec -l "/boot/linux-4.9.10" --console-serial \
-        --initrd="/boot/initramfs-sysb.cpio.gz" \
-        --append="init=/init console=ttyS0"
-    echo "kexecing into sysb"
-    kexec -e
+    if [ "${KERNEL_BOOTSTRAP}" = True ]; then
+        kexec-linux "/dev/ram1" "/boot/linux-4.9.10" "/boot/initramfs-sysb.cpio.gz"
+    else
+        # Mount proc for kexec
+        mkdir /proc /etc
+        mount -t proc proc /proc
+        # kexec time
+        echo "Loading kernel + sysb initramfs using kexec"
+        kexec -l "/boot/linux-4.9.10" --console-serial \
+            --initrd="/boot/initramfs-sysb.cpio.gz" \
+            --append="init=/init console=ttyS0"
+        echo "kexecing into sysb"
+        kexec -e
+    fi
 }
 
 build automake-1.15.1
@@ -96,12 +100,7 @@ build musl-1.2.3 '' no-patches
 
 if [ "${CHROOT}" = False ]; then
     create_sysb
-    if [ "${KERNEL_BOOTSTRAP}" = True ]; then
-        echo "Kernel bootstrapping successful."
-        echo "NOTE: Transition to Linux and building remaining packages is under development."
-    else
-        go_sysb
-    fi
+    go_sysb
 else
     # In chroot mode transition directly into System C.
     SYSC=/sysc_image