Add minimal-system-image-x86_64

This element produces a disk image that boots in QEMU. It has a kernel,
BusyBox, and little else; but should be suitable as a basis for more
grand endeavours.

This disk image we produce is 53MB. I spent a while trying to get this
as small as possible and this is as far as I got:

  * The boot partition seems to have a minimum size just over 32MB;
    lower than that and SYSLINUX fails to write the boot sector. The
    combined size of the initramfs and kernel is about 32MB, so I
    imagine that's what limits us.

  * The main partition is limited in size only by the amount of binaries
    that we put there.

  * We have a useless 40KB swap partition, which the x86image plugin
    insists on creating for us. Again 40KB is the minimum size that
    `mkswap` will allow. It's possible to override or modify the
    x86image plugin to avoid swap altogether but I'm not sure of the
    best way to proceed.

There are a few dependency cleanups in the bsp-generic stack; previously
we'd build the whole 'foundation' stack which took ages and wasn't
needed at all.

1 files changed, 4 insertions, 1 deletions

diff --git a/elements/bsp-generic/linux.bst b/elements/bsp-generic/linux.bst
index 536d6c1d..bac015a3 100644
--- a/elements/bsp-generic/linux.bst
+++ b/elements/bsp-generic/linux.bst
@@ -1,6 +1,9 @@
 kind: manual
+
 depends:
-- docutils.bst
+- filename: core.bst
+  type: build
+
 sources:
 - kind: git
   url: upstream:linux