--- a/build/build-clang/build-clang.py
+++ b/build/build-clang/build-clang.py
@@ -574,12 +574,10 @@ if __name__ == "__main__":
             llvm_source_dir, stage3_dir, build_libcxx, osx_cross_compile,
             build_type, assertions, python_path, gcc_dir, libcxx_include_dir)
 
     package_name = "clang"
     if build_clang_tidy:
         prune_final_dir_for_clang_tidy(os.path.join(final_stage_dir, "clang"))
         package_name = "clang-tidy"
 
-    if is_darwin() or is_windows():
-        build_tar_package("tar", package_name + ".tar.bz2", final_stage_dir, "clang")
-    else:
-        build_tar_package("tar", package_name + ".tar.xz", final_stage_dir, "clang")
+    ext = "bz2" if is_darwin() or is_windows() else "xz"
+    build_tar_package("tar", "%.tar.%s" % (package_name, ext), final_stage_dir, "clang")