Build natively using setarch for i586/armv7
Context
Currently, the builds for i586 and armv7 are done on x86_64 and aarch64 machines respectively. This is considered cross-compilation even if the machines in question can run i586 or armv7 binaries.
Cross compilation is painful at best, and sometimes some features are unavailable. For instance, in gnome-build-meta, after fighting with some build/toolchain options, I got Webkit to build on arm. However, introspection is disabled when cross-compiling. I can go on and patch it, but I feel it would be just better if we aren't cross-compiling.
Description
Since the x86_64 runners can run i586 (obviously) and the aarch64 runner we use for armv7 can run armv7 binaries, we can use setarch
to make the build think it is actually running on the desired architecture.