chore: checkpoint before Python removal

vendor/schemars/build.rs

@@ -0,0 +1,25 @@
+use std::env;
+
+// Based on https://github.com/serde-rs/serde/blob/master/serde/build.rs
+
+fn main() {
+    let target = env::var("TARGET").unwrap();
+    let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
+
+    // Whitelist of archs that support std::sync::atomic module. Ideally we
+    // would use #[cfg(target_has_atomic = "...")] but it is not stable yet.
+    // Instead this is based on rustc's src/librustc_target/spec/*.rs.
+    let has_atomic64 = target.starts_with("x86_64")
+        || target.starts_with("i686")
+        || target.starts_with("aarch64")
+        || target.starts_with("powerpc64")
+        || target.starts_with("sparc64")
+        || target.starts_with("mips64el");
+    let has_atomic32 = has_atomic64 || emscripten;
+    if has_atomic64 {
+        println!("cargo:rustc-cfg=std_atomic64");
+    }
+    if has_atomic32 {
+        println!("cargo:rustc-cfg=std_atomic");
+    }
+}