title: Pass argument from ctest to gtest
body: <p>I am using gtest to write unit tests for my application. I also have ctest that runs all executables added by add_test CMake command. Is it possible to pass gtest variables through ctest when test execution starts?</p>
  
  <p>I would like to for example sometimes filter out tests with --gtest_filter flag but I don't know how or if this is even possible through ctest? I have tried the following ways:</p>
  
  <pre><code>ctest --gtest_filter=AppTest.*
  ctest --test-arguments="--gtest_filter=AppTest.*"
  </code></pre>
  
  <p>But both still run all tests instead the filtered ones.</p>
  
  <p>Thanks!</p>