Add pre-built attribute to host module definition for fake snapshot.

The host-snapshot provides host tools via prebuilt modules.
Having 2 prebuilts of the same module in a source tree leads to a build
time error.   Add new attribute when building the fake snapshot to
indicate that the host tool contains a prebuilt version.

When installing the host snapshot the user can opt not to include
modules that have a prebuilt version.

Bug: 225890931
Test: m HOST_FAKE_SNAPSHOT_ENABLE=true host-fake-snapshot dist
Change-Id: I044a92a280536f9c5ec93dcb277a5e5568cc4e42