[bug#34304] [PATCH] doc: Document how to enable qemu binfmt service and how to use it.

[Ricardo Wurmus <rekado@elephly.net>]

Danny Milosavljevic <dannym@scratchpost.org> writes:

> * doc/contributing.texi (Submitting Patches): Document how to enable qemu
> binfmt service and how to use it.

Sounds good to me!

> +We recommend you also try to build the package on other platforms.  We
> +do not presume that you have all the platforms, therefore we recommend
> +using the qemu binfmt service of GuixSD.  In order to enable it, add
> +the following service to your operating-system configuration's services:

How about this:

--8<---------------cut here---------------start------------->8---
We recommend you also try building the package on other supported
platforms.  As you may not have access to actual hardware platforms, we
recommend using the @code{qemu-binfmt-service-type} to emulate them.  In
order to enable it, add the following service to the list of services in
your @code{operating-system} configuration:
--8<---------------cut here---------------end--------------->8---


> +You can then build packages like the following, respectively:
> +@example
> +guix build --system=armhf-linux --rounds=2 my-package
> +guix build --system=aarch64-linux --rounds=2 my-package
> +guix build --system=powerpc-linux --rounds=2 my-package
> +guix build --system=mips64el-linux --rounds=2 my-package
> +@end example

How about:

--8<---------------cut here---------------start------------->8---
You can then build packages for different platforms by specifying the
@code{--system} option.  For example, to build the “hello” package for
the armhf, aarch64, powerpc, or mips64 architectures, you would run the
following commands, respectively:
@example
guix build --system=armhf-linux --rounds=2 hello
guix build --system=aarch64-linux --rounds=2 hello
guix build --system=powerpc-linux --rounds=2 hello
guix build --system=mips64el-linux --rounds=2 hello
@end example
--8<---------------cut here---------------end--------------->8---