Extend CompileSteps collection

[llogick]

Recent changes to the MicroZig, 👋, builds proved the current CompileSteps collection isn't thorough, eg for a MicroZig project that only had

		mb.install_firmware(fw, .{});
		// but not also
		// mb.install_firmware(fw, .{ .format = .elf });

the build_runner would fail to collect any CompileSteps.

The new logic also pushes local CompileSteps, ie nearest to the current build.zig, and those with most modules towards the top.