Whitelist future LibreSSL 2.9.x versions, as 2.9.1 is the first stable release.

openssl-sys/build/main.rs

@@ -199,7 +199,7 @@ See rust-openssl README for more information:
             (8, 1) => ('8', '1'),
             (8, _) => ('8', 'x'),
             (9, 0) => ('9', '0'),
-            (9, 1) => ('9', '1'),
+            (9, _) => ('9', 'x'),
             _ => version_error(),
         };
 
@@ -240,7 +240,7 @@ fn version_error() -> ! {
         "
 
 This crate is only compatible with OpenSSL 1.0.1 through 1.1.1, or LibreSSL 2.5
-through 2.9.1, but a different version of OpenSSL was found. The build is now aborting
+through 2.9.x, but a different version of OpenSSL was found. The build is now aborting
 due to this version mismatch.
 
 "