pw_presubmit: add QEMU as a broken presubmit check
pw_presubmit: add QEMU as a broken presubmit check

Adds QEMU as a broken presubmit check so CQ can build the QEMU target as
an experimental build until it is fixed and can be added to blocking CQ
builds.

Change-Id: Ie88aea4c674384fcf507b8e5272afb7558ab7288

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed