[Driver] Add option to print the resource directory

This patch adds the option -print-resource-dir. It simply
prints the resource directory. This information will eventually
be used in compiler-rt to setup COMPILER_RT_LIBRARY_INSTALL_DIR.

Patch by Catherine Moore!

Differential Revision: https://reviews.llvm.org/D31447

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@299473 91177308-0d34-0410-b5e6-96231b3b80d8