Delay platform availability error for ALLOW_MISSING_DEPENDENCIES=true

The platform availability check was erroring incorrectly for the
libstatssocket module in master-art-host builds.  Nothing being
built depended on libstatssocket, but the check would still
error because libstatspull_test was defined in the branch but
unused in the build.

When ALLOW_MISSING_DEPENDENCIES=true is set and a module fails
the check add an additional dependency on a rule that prints
the error message.  This will show the error and fail the build
if an unavailable module is requested to be installed, while
allowing the build to proceed if there are no unavailable
modules in the dependency graph.

Fixes: 154888298
Test: m build-art-host TARGET_BUILD_UNBUNDLED=true ALLOW_MISSING_DEPENDENCIES=true libstatspull_test -k
Test: m build-art-host TARGET_BUILD_UNBUNDLED=true ALLOW_MISSING_DEPENDENCIES=true
Change-Id: I1d57afe60a75d65128e59f794243a0414cbc82f6