chore: checkpoint before Python removal

vendor/icu_normalizer_data/build.rs

@@ -0,0 +1,11 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+fn main() {
+    if std::env::var("ICU4X_DATA_DIR").is_ok() {
+        println!("cargo:rustc-cfg=icu4x_custom_data");
+    }
+    println!("cargo:rerun-if-env-changed=ICU4X_DATA_DIR");
+    println!("cargo:rustc-check-cfg=cfg(icu4c_enable_renaming)");
+}