Make it work with older versions of Rust.

rsplit_once was introduced in rustc v1.52.

Author: jfgoog

src/lib.rs

@@ -3616,8 +3616,8 @@ static NEW_STANDALONE_ANDROID_COMPILERS: [&str; 4] = [
 fn android_clang_compiler_uses_target_arg_internally(clang_path: &Path) -> bool {
     if let Some(filename) = clang_path.file_name() {
         if let Some(filename_str) = filename.to_str() {
-            if let Some((target, _)) = filename_str.rsplit_once("-") {
-                return target.contains("android");
+            if let Some(idx) = filename_str.rfind("-") {
+                return filename_str.split_at(idx).0.contains("android");
             }
         }
     }