Fix conv_linker_config with multiple input json files

`conv_linker_config proto -s` should work with multiple json input
files, but ParseDict() overwrites list fields (e.g. provideLibs), not
appending elements.

Also added a test.

Bug: 264330513
Test: conv_linker_config_test
Change-Id: Idc482f941201f15e5fc276c0ffc0dfeaa09d0cc2
diff --git a/scripts/Android.bp b/scripts/Android.bp
index 5dd45cd..ddbba74 100644
--- a/scripts/Android.bp
+++ b/scripts/Android.bp
@@ -191,6 +191,17 @@
     ],
 }
 
+python_test_host {
+    name: "conv_linker_config_test",
+    main: "conv_linker_config_test.py",
+    srcs: [
+        "conv_linker_config_test.py",
+        "conv_linker_config.py",
+    ],
+    libs: ["linker_config_proto"],
+    test_suites: ["general-tests"],
+}
+
 python_binary_host {
     name: "get_clang_version",
     main: "get_clang_version.py",