flutter-auto: disable webview plugin on 32-bit ARM

flutter-auto: disable webview plugin on 32-bit ARM

Disable building the webview plugin on 32-bit ARM, as it has been
seen to fail on qemuarm and beaglebone.  This should be checked
in the future when meta-flutter or meta-clang are updated.

Bug-AGL: SPEC-5266

Change-Id: I9397a7b69a8935a4033e5da17419602555519453
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/30442
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
ci-image-boot-test: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
Tested-by: Jenkins Job builder account