Revert "Revert "[cmake] [compiler-rt] Call llvm_setup_rpath() when adding shared libraries.""

This reverts commit 21c008d5 since
it broke the build on macOS and Windows with the following error:

  The install of the clang_rt.<na,e> target requires changing an
  RPATH from the build tree, but this is not supported with the Ninja
  generator unless on an ELF-based platform.  The
  CMAKE_BUILD_WITH_INSTALL_RPATH variable may be set to avoid this relinking
  step.