libavr_format_test()

# The battery is a compile: a static_assert that fails is the failure. It is a
# target rather than only a ctest so a plain build catches a regression too.
add_library(consteval_tests OBJECT consteval.cpp)
target_link_libraries(consteval_tests PRIVATE ds3231)

add_test(NAME ds3231.consteval
         COMMAND ${CMAKE_COMMAND} --build ${CMAKE_BINARY_DIR} --target consteval_tests)