Implement fallback to compiling serde_derive from source

precompiled/serde_derive/src/lib_from_source.rs

@@ -0,0 +1,39 @@
+#[macro_use]
+extern crate quote;
+#[macro_use]
+extern crate syn;
+
+extern crate proc_macro2;
+
+mod internals;
+
+use proc_macro::TokenStream;
+use syn::DeriveInput;
+
+#[macro_use]
+mod bound;
+#[macro_use]
+mod fragment;
+
+mod de;
+mod dummy;
+mod pretend;
+mod ser;
+mod this;
+mod try;
+
+#[proc_macro_derive(Serialize, attributes(serde))]
+pub fn derive_serialize(input: TokenStream) -> TokenStream {
+    let mut input = parse_macro_input!(input as DeriveInput);
+    ser::expand_derive_serialize(&mut input)
+        .unwrap_or_else(syn::Error::into_compile_error)
+        .into()
+}
+
+#[proc_macro_derive(Deserialize, attributes(serde))]
+pub fn derive_deserialize(input: TokenStream) -> TokenStream {
+    let mut input = parse_macro_input!(input as DeriveInput);
+    de::expand_derive_deserialize(&mut input)
+        .unwrap_or_else(syn::Error::into_compile_error)
+        .into()
+}