[Clang][clang-nvlink-wrapper] Pass nvlink path to the wrapper

Added support of a "--nvlink-path" option in clang-nvlink-wrapper which
takes the path of nvlink binary.

Static Device Library support for OpenMP (D105191) now searches for
nvlink binary and passes its location via this option. In absence
of this option, nvlink binary is searched in locations in PATH.

Differential Revision: https://reviews.llvm.org/D111488