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

This reverts commit 21c008d 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.

Author: petrhosek

compiler-rt/cmake/Modules/AddCompilerRT.cmake

@@ -359,6 +359,9 @@ function(add_compiler_rt_runtime name type)
       target_link_libraries(${libname} PRIVATE ${builtins_${libname}})
     endif()
     if(${type} STREQUAL "SHARED")
+      if(COMMAND llvm_setup_rpath)
+        llvm_setup_rpath(${libname})
+      endif()
       if(WIN32 AND NOT CYGWIN AND NOT MINGW)
         set_target_properties(${libname} PROPERTIES IMPORT_PREFIX "")
         set_target_properties(${libname} PROPERTIES IMPORT_SUFFIX ".lib")