Add experiment to produce precompiled builds of serde_derive

precompiled/Cargo.toml

@@ -0,0 +1,14 @@
+[workspace]
+members = ["proc-macro2", "serde_derive"]
+resolver = "2"
+
+[patch.crates-io]
+proc-macro2 = { path = "proc-macro2" }
+
+[profile.precompiled]
+inherits = "release"
+codegen-units = 1
+lto = true
+opt-level = "z"
+panic = "abort"
+strip = true