CMAKE_<LANG>_LINK_DEF_FILE_FLAG

在 4.1 版被加入.

Linker flag to be used to specify a .def file for dll creation with the toolchain for language <LANG>.

CMake sets this variable automatically during toolchain inspection by calls to the project() or enable_language() commands.

If the CMAKE_<LANG>_LINK_DEF_FILE_FLAG variable is defined, it takes precedence over the language-agnostic CMAKE_LINK_DEF_FILE_FLAG variable.