Component Debugger: don't hardcode net fx compiler

[chsienki]

Currently we hardcode the location of the compiler used to debug by looking it up in a well known location in the VS directory. We also only support debugging of the desktop net fx compiler.

We should instead calculate the compiler to use based on the msbuild properties, so that when debugging we're debugging using the same version of the compiler as will actually be used to build the project.