This generalizes handling of the integration tests. We now implicitly
depend on the `libc.startup.${LIBC_TARGET_OS}.crt1` file rather than
passing it in manually. This simplifies the interface.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D146237
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.