cmake + gtest_discover_tests not working, path is not set

In CMake there's a new feature to scan for unit tests, it's called gtest_discover_tests() in the GoogleTest module. This works by calling the created test executable just after linking. The test executable will return a list of all tests it contains. However, the system environment is not set correctly at this stage, the appropriate Qt library is not in the path. So if the test executable contains Qt code, it will never work, because it can't find the Qt dlls and will immediately die with error code 0xc0000135 (library not found). In my case, only "C:\Qt\Qt5.9.5\Tools\mingw530_32\bin" appears to be prepended to the path.