build: Disable nacl when building for mac on different hosts

nacl needs mig,  We could do something like the changes on bug 1202978
for nacl too, but just disabling it is probably sufficient.

While here, more explicitly disable nacl for mac/arm64. That part is
not a behavior change, but it makes it less likely we'll accidentally
turn it on there should we ever ship nacl for arm64 on some other
platform one day.

Bug: 1147069,1202978
Change-Id: I2ca4896b6a6df8aaf90ef62fab6ba5c42fe96f4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3237628
Auto-Submit: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/main@{#934210}