lacros: Make nacl_bootstrap toolchain work with `lacros_use_chromium_toolchain = true`

In native_client/src/trusted/service_runtime/linux/BUILD.gn,
nacl_bootstrap_lib removes all configs and then adds back
only a select few. It doesn't add back build/config/compiler,
only build/config/compiler:compiler_cpu_abi. So put the config
that sets the lacros --target flags into compiler_cpu_abi.
Else, we fail to build the nacl_bootstrap target for arm in
lacros device arm chromium toolchain builds.

Follow-up to https://chromium-review.googlesource.com/c/chromium/src/+/3703623

Bug: 1169197
Change-Id: I535dfe3ef22feb0879d2cfc285da02fa3d49a853
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3707654
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1014500}
NOKEYCHECK=True
GitOrigin-RevId: 70e6e8d4b62014fb59a6ec127837244d3b79ce96
2 files changed