wic: Add RootfsPlugin

Implement RootfsPlugin class. The do_prepare_partition() method
is implemented using code in Wic_PartData class.

This class have 'rootfs' name, which is the name that should
be used in the --source parameters of the .wks partition commands.

Signed-off-by: João Henrique Ferreira de Freitas <joaohf@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
wic: Hook up RootfsPlugin plugin

Remove the 'rootfs' case when internal call code is used and
replace to call the general-purpose plugin.

For now RootfsPluing class continues to invoke prepare_rootfs()
method from Wic_PartData. However RootfsPlugin could implement them.

Signed-off-by: João Henrique Ferreira de Freitas <joaohf@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
wic: Add rootfs_dir argument to do_prepare_partition() method

The do_prepare_partition() method from RootfsPlugin class need
to know what will be the rootfs_dir. This makes sense when .wks
file has a partition set up like this:

  part /standby --source rootfs --rootfs=<special rootfs> ...

then do_prepare_partition() will work with the correct rootfs.

Signed-off-by: João Henrique Ferreira de Freitas <joaohf@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
wic: Use partition label to be part of rootfs filename

When a partition from .wks file is set up like this:

  part /standby --source rootfs --rootfs=<special rootfs> ... --label \
    --label secondary

This means that 'rootfs' must use '<special rootfs>' as rootfs and
the default partition filename in /var/tmp/wic/build/ will be create
using the '--label' as part of the name. E.g:

  /var/tmp/wic/build/rootfs_secondary.ext3

Signed-off-by: João Henrique Ferreira de Freitas <joaohf@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
wic: Add option --rootfs to --source

The '--rootfs' option is optional and only takes efect is a
partition is set up like this:

  part /standby --source rootfs --rootfs=<special rootfs> ...

So '--rootfs' is used instead of bitbake ROOTFS_DIR variable or
'-r' param.

Signed-off-by: João Henrique Ferreira de Freitas <joaohf@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
acpica: Add recipe for latest version

This is now used by multiple architectures and is useful when working
with firmware. I'd love to see more BSPs shipping working firmware
builds and this should bring us a step closer to that.

(From OE-Core rev: 014b719b0a138bea2e13adb85a84497cbc2027a3)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
autotools: Enable separate builddir by default

(From OE-Core rev: 4c426fe75866f9d27f84971e23440bf6c7e23fb6)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>