Add ability to pass in a config string for FRROs

This enables passing them and and storing them in the .frro file but no
further.

Bug: 243066074
Test: Manual
Change-Id: I5c9723e69d175a536f9739619c6b6bf3162a5027
diff --git a/cmds/idmap2/tests/ResourceMappingTests.cpp b/cmds/idmap2/tests/ResourceMappingTests.cpp
index c05abcf..ca9a444 100644
--- a/cmds/idmap2/tests/ResourceMappingTests.cpp
+++ b/cmds/idmap2/tests/ResourceMappingTests.cpp
@@ -194,9 +194,9 @@
 TEST(ResourceMappingTests, FabricatedOverlay) {
   auto frro = FabricatedOverlay::Builder("com.example.overlay", "SandTheme", "test.target")
                   .SetOverlayable("TestResources")
-                  .SetResourceValue("integer/int1", Res_value::TYPE_INT_DEC, 2U)
-                  .SetResourceValue("string/str1", Res_value::TYPE_REFERENCE, 0x7f010000)
-                  .SetResourceValue("string/str2", Res_value::TYPE_STRING, "foobar")
+                  .SetResourceValue("integer/int1", Res_value::TYPE_INT_DEC, 2U, "")
+                  .SetResourceValue("string/str1", Res_value::TYPE_REFERENCE, 0x7f010000, "")
+                  .SetResourceValue("string/str2", Res_value::TYPE_STRING, "foobar", "")
                   .Build();
 
   ASSERT_TRUE(frro);