aconfig: improve code diffs in tests

Implement a helper function to make it easier for unit tests to diff
(and find the first difference) generated code and expected code.

Bug: 283910447
Test: atest aconfig.test
Change-Id: I460e8fbf05e8f33e8a62ecef67b2d9d77051e876
diff --git a/tools/aconfig/Android.bp b/tools/aconfig/Android.bp
index 9617e0e..b8cce29 100644
--- a/tools/aconfig/Android.bp
+++ b/tools/aconfig/Android.bp
@@ -35,4 +35,7 @@
 rust_test_host {
     name: "aconfig.test",
     defaults: ["aconfig.defaults"],
+    rustlibs: [
+        "libitertools",
+    ],
 }