Workaround rust 1.38 pipelined compilation (#67)

lu-zero · est31 · commit f7bb469786ab · 2019-09-27T01:36:01.000+02:00
It breaks `cargo-c` otherwise.
diff --git a/Cargo.toml b/Cargo.toml
@@ -38,3 +38,4 @@ features = ["async_ogg"]
 
 [lib]
 name = "lewton"
+crate-type = ["lib", "staticlib"]
