meson/docs/markdown/snippets/compiler_has_define.md

Compilers now have a has_define method

This method returns true if the given preprocessor symbol is defined, else false is returned. This is useful is cases where an empty define has to be distinguished from a non-set one, which is not possible using get_define.

Additionally it makes intent clearer for code that only needs to check if a specific define is set at all and does not care about its value.