Test: add java source files as JavaSourceRoot

so that those can be properly populated in SingleJavaRootsIndex

compiler/testData/diagnostics/tests/smartCasts/toInvisible.fir.kt

@@ -33,7 +33,7 @@ import a.AImpl
 fun test1(a: A) {
     if (a is AImpl) {
         (a as A).b().bar() // OK
-        a.b().<!UNRESOLVED_REFERENCE!>bar<!>()
+        a.b().<!INVISIBLE_REFERENCE!>bar<!>()
     }
 }