* The macro is tested with #if/#ifdef/#ifndef/#elif in a source file
outside of config/ (but including front-end subdirectories). Care is
needed in identifying such macros through grep because of
backslash-newline line continuations and because it's possible some macros
are only tested in generated files not directly in source files. Of
course lots of macros tested in preprocessor conditionals will not be
target macros, but you need to check the definitions of such macros to
find any cases such as:
#define FOO TARGET_MACRO
#if FOO