Fix CI fails after switching to `gtest_discover_tests`

[adamkewley]

This action fails:

• https://github.com/ComputationalBiomechanicsLab/opensim-creator/actions/runs/6352101783

With this error:

   testoscar.vcxproj -> D:\a\opensim-creator\opensim-creator\osc\osc-build\tests\testoscar\RelWithDebInfo\testoscar.exe
  CMake Error at C:/Program Files/CMake/share/cmake-3.27/Modules/GoogleTestAddTests.cmake:112 (message):
    Error running test executable.

      Path: 'D:/a/opensim-creator/opensim-creator/osc/osc-build/tests/testoscar/RelWithDebInfo/testoscar.exe'
      Result: Exit code 0xc0000135

      Output:

Because of this changeset ("works on my machine"):

• https://github.com/ComputationalBiomechanicsLab/opensim-creator/commit/55c7057d6393f6bbbfed4b52784f33d9ff2f58e6

And I believe (not confirmed) the reason why is because gtest_discover_tests runs the binary before my "copy runtime DLLs" POST_BUILD action, which is necessary for running windows executables because they don't have an rpath etc.:

• https://github.com/ComputationalBiomechanicsLab/opensim-creator/blob/b23c037/tests/TestOpenSimCreator/CMakeLists.txt#L46

Thanks to @zonmen for mentioning the idea of this being the problem on a googletest issue:

• https://github.com/google/googletest/issues/3565

[adamkewley]

Adding PRE_TEST didn't fix it :(

[adamkewley]

The fix for this was to tell CMake exactly which TARGET_RUNTIME_DLLS are needed on Windows, and to make the build command copy the runtime binaries in a PRE_BUILD step