Unconditionally add AllocTokenPass to the optimization pipelines, and
ensure that it runs last in LTO backend pipelines. The latter ensures
that AllocToken instrumentation can be moved later in the LTO pipeline
to avoid interference with other optimizations (e.g. PGHO) and enable
late heap-allocation optimizations.
In preparation of removing AllocTokenPass being added by Clang, add
support for AllocTokenPass to read configuration options from LLVM
module flags.
To optimize given the pass is now runs unconditionally, only retrieve
TargetLibraryInfo and OptimizationRemarkEmitter when necessary.
96c69b7393