Add testing utility function for buildErrHandler

Testing functions that call into the build handler is currently a bit fastidious as this handler produces a sequence of API calls. We should add a utility function to make it easier to write tests for functions that use this handler. See discussion on https://github.com/KhronosGroup/OpenCL-CLHPP/pull/102

Start by reading the discussion in OpenCL-CLHPP pull request #102, then inspect how buildErrHandler is used in the repository's tests. Define the utility around the handler's sequence of API calls and confirm that it makes tests for callers easier to write; the issue names no specific file or test to run.

Written by the indexing model from the issue text.