microdroid_vendor implements the vendor.img of microdroid. In theory,
microdroid doesn't need a vendor partition as it by definition isn't
specific to any SoC. However, init demands some files from the vendor
partition during the boot process. Until we find a way to make the
dependencies optional, let's have the vendor partition. Fortunately, it
is very small. It currently has a few number of sepolicy files only.
Bug: 180986662
Test: run microdroid following README.md
init enters into the second stage, sepolicy files are compiled, init
tries to start the servicemanager (which fails)
Change-Id: I82a66a00a8680ef1070ae7313d8e326f3ebc3112