[Bazel] Derive targets from file presence as in CMake build

This makes the logic used to determine if targets have the given
features the same as is used in CMake. Incidentally, it enables these
features for the targets added in https://reviews.llvm.org/D106921
which were missing because this was previously a hardcoded list.

Reviewed By: chandlerc

Differential Revision: https://reviews.llvm.org/D107019