build_cfg is used at run time in 1 crate (of which 1 optionally). It's used at build time in 4 crates (3 directly).

Depender (with downloads and own rev deps) build_cfg version
120 prefer-dynamic build ^1
clippers build ^1
1 clip_img build ^1.1.0
500 3 windows_exe_info optional ^1.1.0