LLVM build system separates between `add_llvm_example_library` and `add_llvm_library`, which is presumably used to package examples separately from the regular library. Introduce a similar approach to building example libraries in MLIR and use it for the transform dialect tutorial. Reviewed By: mehdi_amini Differential Revision: https://reviews.llvm.org/D153265
Transform Dialect Tutorial is available at https://mlir.llvm.org/docs/Tutorials/transform.
Test files are located under mlir/test/Examples/Transform.