[Clang] Do not build the OffloadActionBuilder when using the new driver

The Offloading toolchain currently has two methods for construction the
requires actions. The "new" driver and the old `OffloadActionBuilder`.
Using either one is mutually exclusive, so we should not initialize this
when using the new driver. This was causing some error messages to be
printed multiple times because we were checking them in both the old and
the new driver.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D135715