Use when probing the host/toolchain for capabilities inside `xmake.lua` — `has_cfuncs` / `has_cxxtypes` / `has_features`, `check_csnippets`, `check_cflags` / `check_cxxflags`, option auto-probes (`add_cxxincludes` / `add_cfuncs`), and `lib.detect.find_*`. Covers how to gate target config on whether a symbol/header/flag is actually usable on the target platform.
