Allow cross-build for selected packages about isar

[ismagulb]

Hello Jan,

we have a working implementation for Isar's predecessor. We'll evaluate and let you know. When do you need it?

[jan-kiszka]

Ideally short-term: We will build up a scenario for an ARM board over the next weeks, and accelerated building for kernel or u-boot would be a useful feature. Whatever you can share early would be welcome, but it won't be a blocker not having it.

[flenorm]

Hello Jan,

A proof-of-concept of this feature was implemented and the commits pushed on the lenormf/uefi_wic_amd64-20170428 branch.

For the purpose of testing this branch, an archive of the debianized source code of u-boot v2016.11 was added alongside its corresponding recipe, which ISAR cross-compiles by default. To run a build, use the following commands:

$ source isar-init-build-env b-armhf
$ bitbake multiconfig:qemuarm:isar-image-base

The above generates an armhf image, and cross-compiles a RaspberryPi2 version of u-boot; you can also try cross-compiling an arbitrary package (e.g. hello) by making its recipe inherit from dpkg-cross instead of dpkg only.

[myo73]

Cross-compilation support was added in Release v0.6