Constant openssl_sys::OPENSSL_CFLAGS
pub const OPENSSL_CFLAGS: c_int = 1;
The portability is definied by:
#[cfg(all(any(ossl110, libressl271), not(any())))]
pub const OPENSSL_CFLAGS: c_int = 1;
#[cfg(all(any(ossl110, libressl271), not(any())))]