We currently have an option to select C++ ABI and C++ library for tests
but there are runtimes that use C++ library, specifically ORC and XRay,
which aren't covered by existing options. This change introduces a new
option to control the use of C++ libray for these runtimes.
Ideally, this option should become the default way to select C++ library
for all of compiler-rt replacing the existing options (the C++ ABI
option could remain as a hidden internal option).