The LibreSSL version in -current isn't explicitly supported.

Index: vendor/openssl-sys-0.9.92/build/main.rs
--- vendor/openssl-sys-0.9.92/build/main.rs.orig
+++ vendor/openssl-sys-0.9.92/build/main.rs
@@ -273,7 +273,7 @@ See rust-openssl documentation for more information:
             (3, 7, 1) => ('3', '7', '1'),
             (3, 7, _) => ('3', '7', 'x'),
             (3, 8, 0) => ('3', '8', '0'),
-            _ => version_error(),
+            _ => ('3', '8', '0'),
         };
 
         println!("cargo:libressl=true");
