forked from boostorg/config
See https://github.com/boostorg/config/commit/8dcea4d78c7a9bd07322015d541fb76c77e33022#commitcomment-35718928.
See https://github.com/boostorg/config/commit/8dcea4d78c7a9bd07322015d541fb76c77e33022#commitcomment-35718928.