How to test build using Aboriginal Linux system images.

* Put a source tree into hdc.dir/.
For example, this should work:
git clone git://busybox.net/var/lib/git/busybox.git

* Run ./make-hdc-img.sh: it will generate ext2 image file,
hdc.img, from hdc.dir/* data. This requires root for loop mount.

* Download and unpack, or build from source and unpack
one or more system-image-ARCH directories into this directory
(the one which contains this README).

* Run: ./parallel-build-hdc-img.sh system-image-DIR1 system-image-DIR2...
(background it if you don't want to see "Waiting to finish" thing).
This runs build in several qemu virtual machines in parallel.

* Observe system-image-*.log file(s) with growing log of the build.

There is no automated detection of errors for now: you need to examine
logs yourself.

Log files will also contain uuencoded (or if all else fails, od -tx1'ed)
binary, if build was successful.

To debug a build problem in one of the sandboxes, change keep_hdb
to "keep_hdb=true" in parallel-build-hdc-img.sh
- this preserves system-image-ARCH/hdb.img after the build,
so you can go into system-image-ARCH and run
"HDB=hdb.img ./dev-environment.sh" to debug the problem.

You can also run "./parallel-build-hdc-img.sh -s system-image-ARCH"
- single mode, output is to screen and serial input is from keyboard.

If hdc.dir/bin/busybox-$ARCH exists, it will be used during build
to supply additional tools.

For me, the following system images worked:
system-image-armv4l
system-image-armv4tl
system-image-armv5l
    od is buggy on arm*:
    # echo Hello-hello-hello-hello | od -b
    0000000 110 145 154 154 157 055 150 145 154 154 157 055 150 145 154 154
    0000000 157 055 150 145 154 154 157 012
    0000000
system-image-i686
system-image-mips
system-image-mipsel
    od is buggy on mips[el]:
    # echo Hello-hello-hello-hello | od -b
    0000000 110 145 154 154 157 055 150 145 154 154 157 055 150 145 154 154
    17767153361 157 055 150 145 154 154 157 012
    0000000
system-image-x86_64

And these did not:
system-image-armv6l  - hang on "Uncompressing Linux... done, booting the kernel"
system-image-powerpc - hang early in kernel boot
system-image-sparc   - hang early in userspace
system-image-m68k    - my qemu doesn't like "-M q800"
system-image-mips64  - init dies "Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000a"
system-image-sh4     - qemu segfaults early in kernel boot