Run art_boot before odsign.

It's necessary to have the right dalvik.vm.* flags in place when they
are validated by odrefresh.

Test: See the other CL in the topic.
Bug: 281850017
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7c9c8f52e75daf30ae0cc6130c321769a23e320d)
Merged-In: Ib64790dde97faaa6b62ead2c1c8dd53c97f97f9c
Change-Id: Ib64790dde97faaa6b62ead2c1c8dd53c97f97f9c