Kaleidoscope-Ch7: Add missing transformutils to llvm-config params

[mkroll]

Summary

TransformUtils is needed because of llvm::createPromoteMemoryToRegisterPass

[chapuni]

"x86" (one of "native") may induct TransformUtils, though.

I wonder libraries on llvm-config could describe minimal set, or "Used libraries in toy.cpp"
If the latter, we should give, to llvm-config, LINK_COMPONENTS in llvm/examples/Kaleidoscope/Chapter7/CMakeLists.txt.

That is, I don't think it'd be appropriate just to add TransformUtils to the command line of llvm-config in the doc.

FYI, I recommend LINK_COMPONENTS should describe "Libraries referred from objects to be linked".
In future, clang-modules would help it. (modules should know libs to link)

docs/tutorial/LangImpl07.rst

 =================
 
 Here is the complete code listing for our running example, enhanced with
 mutable variables and var/in support. To build this example, use:
 
 .. code-block:: bash
 
     # Compile
-    clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core mcjit native` -O3 -o toy
+    clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core mcjit native transformutils` -O3 -o toy
     # Run
     ./toy
 
 Here is the code:
 
 .. literalinclude:: ../../examples/Kaleidoscope/Chapter7/toy.cpp
    :language: c++
 
 `Next: Compiling to Object Code <LangImpl08.html>`_