This part of the effort to make all test related pieces into the `test`
directory. This helps is excluding test related pieces in a straight
forward manner if LLVM_INCLUDE_TESTS is OFF. Future patches will also move
the MPFR wrapper and testutils into the 'test' directory.
This is mostly a mechanical change. In a future pass, all tests from
pthread which create threads will also be converted to integration tests.
Some of thread related features are tightly coupled with the loader. So,
they can only be tested with the in-house loader. Hence, going forward, all
tests which create threads will have to be integration tests.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D128381
