* guix/build/zig-build-system.scm (zig-cross-build): New function
(lower): Add cross-compilation support
* guix/build-system/zig.scm (build): Add --target flag with target input
(check): Disable with cross compilation
Change-Id: I5f42ff897bfe00c92c6576900221a15ef210d669
Signed-off-by: Ludovic Courtès <ludo@gnu.org>