Vendor things

third-party/vendor/serde_json/build.rs

@@ -0,0 +1,17 @@
+use std::env;
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    // Decide ideal limb width for arithmetic in the float parser. Refer to
+    // src/lexical/math.rs for where this has an effect.
+    let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
+    match target_arch.as_str() {
+        "aarch64" | "mips64" | "powerpc64" | "x86_64" | "loongarch64" => {
+            println!("cargo:rustc-cfg=limb_width_64");
+        }
+        _ => {
+            println!("cargo:rustc-cfg=limb_width_32");
+        }
+    }
+}