This allows users to specify different genex-based compile flags for
each file in a target, e.g. compiling just a single file with `Od/Ox` in
release builds on Visual Studio.
This is useful for cases like:
add_test(NAME mytest COMMAND mydriver $<TARGET_FILE:myexe>)
set_tests_properties(mytest PROPERTIES
REQUIRED_FILES "$<TARGET_FILE:myexe>"
WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/$<CONFIGURATION>"
)
In this example we require the actual test executable to exist to
run the test in addition to the test driver at argv[0]. Also the
$<CONFIGURATION> expression improves over \${CTEST_CONFIGURATION_TYPE}
because the latter is not normalized for case-sensitive filesystems.
