Fix CMake configuration without tests

[MatthewScholefield]

This solves the following error that occurs when running cmake . -B build (no tests):

CMake Error at CMakeLists.txt:380 (set_property):
  Error evaluating generator expression:

    $<TARGET_FILE_NAME:bin2cpp_unittest>

  No target "bin2cpp_unittest"

[end2endzone]

Hi. Thank you for pointing this one out. I always set this flag since I always needs to run unit tests but most users wont be in this position.

Regarding your change, I think lines 381 (from the original source code) should also be included in your new "if" block. The wix shortcut to generate_test_files.bat is used for generating unit test files and won't be generated either if you did not set option BIN2CPP_BUILD_TEST. It should be skipped as well.

If you do not want to make the change, I will take care of it myself. I am already glad that you contributed and found more issues and helped a lot.

If you do make changes, could you also do a force-push again to also include the latest changes from master to have all checks to run ?