lacros: Better flags in `lacros_use_chromium_toolchain = true` builds

1. Do not pass two --target flags in arm device builds
2. Do pass --target flags for .S files as well

This is one of two changes needed to make lacros/device/arm device
builds build with `lacros_use_chromium_toolchain = true`. (I haven't
tried running them yet.)

Bug: 1169197
Change-Id: Id42c38554b3d471e0bf47aed9273a2dab6a43763
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3703623
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1014182}
NOKEYCHECK=True
GitOrigin-RevId: 383af7737c7d35f4273b60a1435a6352e513bfa2
2 files changed