https://github.com/sfackler/rust-openssl/pull/2287

Index: vendor/openssl-0.10.57/src/conf.rs
--- vendor/openssl-0.10.57/src/conf.rs.orig
+++ vendor/openssl-0.10.57/src/conf.rs
@@ -8,7 +8,7 @@ foreign_type_and_impl_send_sync! {
     pub struct ConfRef;
 }
 
-#[cfg(not(boringssl))]
+#[cfg(not(any(boringssl,libressl400)))]
 mod methods {
     use super::Conf;
     use crate::cvt_p;
@@ -61,5 +61,5 @@ mod methods {
         }
     }
 }
-#[cfg(not(boringssl))]
+#[cfg(not(any(boringssl,libressl400)))]
 pub use methods::*;
