Add support for CMake generators when installing dependencies.

[jayhawk-commits]

• cget tool supports -G parameter to specify generator. Reference
• This code change provides capability to leverage that support and let user pick a generator with install_deps.cmake, limiting to Ninja or Unix Makefiles at the moment.
• Example Usage: cmake -P install_deps.cmake --prefix $(HOME))/miopen-deps --generator Ninja
• Trial run on Azure VM with 64 cores cut down execution time of this script by a few minutes. Pipeline Log