CTest, CMake & MinGW: Executables build, but fail to run, because fresh DLL is not found

The top-level CMakeLists.txt contains:

include(CTest)add_subdirectory(lib)add_subdirectory(demo)add_subdirectory(test)

lib/CMakeLists.txt is essentially:

add_library(MyLib <sources>)

demo/CMakeLists.txt is essentially:

add_executable(Demo demo.c)target_link_libraries(Demo MyLib)

test/CMakeLists.txt is just:

add_test(NAME Demo COMMAND Demo)

From a gitlab-runner, we execute:

cmake -G "Ninja" -DCMAKE_INSTALL_PREFIX=C:\opt\x64 -B. ..cmake --buildctest --output-on-failure

The first two steps succeed; the third one fails with:

Start 1: Demo1/1 Test #1: Demo .......................Exit code 0xc0000135***Exception:   0.03 sec

If I retry:

cmake --installctest

then the test succeeds. So the sole problem is that build/lib/mylib.dll is not found when running ctest. Whereas C:\opt\x64\lib is in PATH, and therefore the DLL is found after cmake --install. Which, however, is not what we want: ctest shall always use the fresh DLL from the current build, not the installed version.

Under Linux, everything works correctly. Why doesn't it for Windows and MinGW? Is this a bug in CMake? How can we work around this so that ctest executes correctly on all platforms?