Create coverage build configs with cmake

CoverageConfig.cmake

function(extend_custom_config_flags added_conf original_conf flags)
    set(CMAKE_C_FLAGS_${added_conf} "${CMAKE_C_FLAGS_${original_conf}} ${flags}" CACHE STRING "" FORCE)
    set(CMAKE_CXX_FLAGS_${added_conf} "${CMAKE_CXX_FLAGS_${original_conf}} ${flags}" CACHE STRING "" FORCE)
    set(CMAKE_EXE_LINKER_FLAGS_${added_conf} "${CMAKE_EXE_LINKER_FLAGS_${original_conf}} ${flags}" CACHE STRING "" FORCE)
    set(CMAKE_SHARED_LINKER_FLAGS_${added_conf} "${CMAKE_SHARED_LINKER_FLAGS_${original_conf}} ${flags}" CACHE STRING "" FORCE)
    set(CMAKE_MODULE_LINKER_FLAGS_${added_conf} "${CMAKE_MODULE_LINKER_FLAGS_${original_conf}} ${flags}" CACHE STRING "" FORCE)
    set(CMAKE_STATIC_LINKER_FLAGS_${added_conf} "${CMAKE_STATIC_LINKER_FLAGS_${original_conf}} " CACHE STRING "" FORCE)
endfunction()

if(True)
    set(CMAKE_CONFIGURATION_TYPES Debug Release DebugCoverage ReleaseCoverage)
    set(CMAKE_CONFIGURATION_TYPES "${CMAKE_CONFIGURATION_TYPES}" CACHE STRING "List of supported configurations.")
    mark_as_advanced(CMAKE_CONFIGURATION_TYPES)

    extend_custom_config_flags(DEBUGCOVERAGE DEBUG "--coverage")
    extend_custom_config_flags(RELEASECOVERAGE RELEASE "--coverage")
endif()

# prevent spam
set_property(GLOBAL PROPERTY CTEST_TARGETS_ADDED 1)