Re: The 'cross' directory

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Stallman <rms@gnu.org>
> Cc: eliz@gnu.org, emacs-devel@gnu.org
> Date: Sat, 12 Aug 2023 21:43:31 -0400
> 
>   > Nothing broke it.  Emacs never supported cross compilation in the past,
>   > since Emacs is needed on the build machine to compile Lisp and dump
>   > itself.
> 
> In the past, building Emacs was cleanly separated into building
> `temacs' and then using it to dump.  We included .elc files in the tar
> ball so that users did not need to compile any Lisp code unless they
> changed Lisp source.  (Byte-compiling Lisp code was slow and the .elc
> files were portable.)
> 
> So I think it should have worked to make `temacs' cross-compiling
> and then run the rest on the target machine.  That should have been
> easy because it did not need to compile or link any C code.

This should still work, although I doubt if anyone tried it lately.
Emacs with native-compilation cannot be built that way, because the
native-code *.eln files are produced at build time, and cannot be
included in the tarball (they depend on the architecture of the target
machine and include signatures of the Emacs binary and the location of
the source *.el files).  But Emacs without native-compilation could be
produced in such two steps, except that the target environment still
needs some support tools: GNU Make, cp and rm.  (Alternatively, they
could invoke the final build commands by hand, if they know how.)

But I don't believe this is relevant to the Android build, since the
Android development tools don't run on Android, and the Android port
produces an undumped Emacs anyway.