Can't build on linux/aarch64

I'm one of those horrible M1 Mac users screwing up the buildchain for every open source projects. So let me begin by thanking you for abstracting macos/darwin builds so they're architecture independent. It would be great if we could do the same for Linux.

Things work fine in MacOS. It gets _interesting_ when we involve Docker.

Containers can be built for multiple architectures (e.g. x86_64 & aarch64). Docker can run either architecture, though it prefers the native architecture of the host machine. So if an ARM/aarch64 mac tries to build zetasql inside a (local default) aarch64 container, it'll fail, as linux-specific builds are tied to:

`"@bazel_tools//src/conditions:linux_x86_64"`

While mac/darwin builds are configured to use:

`"@bazel_tools//src/conditions:darwin"` or `"@platforms//os:macos"`

It would be nice if linux builds could be configured independent of cpu architecture, or at least could select for linux_aarch64.