Set test config of Robolectric tests to `LOCAL_FULL_TEST_CONFIG`

Downstream infra needs this information to determine if a module is
testable to TradeFed.

Test: m out/target/product/coral/module-info.json
Bug: 268670243
Change-Id: Ibdf99c86cb6abe726552a6e4ffbdc756f751907b
diff --git a/java/robolectric.go b/java/robolectric.go
index 68f27b8..008b8b1 100644
--- a/java/robolectric.go
+++ b/java/robolectric.go
@@ -302,6 +302,9 @@
 		func(ctx android.AndroidMkExtraEntriesContext, entries *android.AndroidMkEntries) {
 			entries.SetBool("LOCAL_UNINSTALLABLE_MODULE", true)
 			entries.AddStrings("LOCAL_COMPATIBILITY_SUITE", "robolectric-tests")
+			if r.testConfig != nil {
+				entries.SetPath("LOCAL_FULL_TEST_CONFIG", r.testConfig)
+			}
 		})
 
 	entries.ExtraFooters = []android.AndroidMkExtraFootersFunc{