Use derive feature of serde

Author: h-michael

src/tools/build-manifest/Cargo.toml

@@ -6,5 +6,5 @@ edition = "2018"
 
 [dependencies]
 toml = "0.4"
-serde = "1.0"
+serde = { version = "1.0", features = ["derive"] }
 serde_derive = "1.0"

src/tools/build-manifest/src/main.rs

@@ -1,7 +1,7 @@
 #![deny(rust_2018_idioms)]
 
 use toml;
-use serde_derive::Serialize;
+use serde::Serialize;
 
 use std::collections::BTreeMap;
 use std::env;