Save updated roots before a packagePartProvider is created

Since the function createPackagePartProvider uses initialRoots for
creating packagePartsProvider, if the updateClasspath function
was called before createPackagePartProvider, the provider was created
with incomplete list of roots, that leaded to the unresolved top-level
functions.
Now if no providers are created yet, the initialRoots is updated.
This still may lead to the inconsistencies, when/if we'll have several
providers.

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/KotlinCoreEnvironment.kt

@@ -159,7 +159,7 @@ class KotlinCoreEnvironment private constructor(
     private val packagePartProviders = mutableListOf<JvmPackagePartProvider>()
 
     private val classpathRootsResolver: ClasspathRootsResolver
-    private val initialRoots: List<JavaRoot>
+    private val initialRoots = ArrayList<JavaRoot>()
 
     val configuration: CompilerConfiguration = initialConfiguration.apply { setupJdkClasspathRoots(configFiles) }.copy()
 
@@ -217,7 +217,7 @@ class KotlinCoreEnvironment private constructor(
 
         val (initialRoots, javaModules) =
                 classpathRootsResolver.convertClasspathRoots(configuration.getList(CLIConfigurationKeys.CONTENT_ROOTS))
-        this.initialRoots = initialRoots
+        this.initialRoots.addAll(initialRoots)
 
         if (!configuration.getBoolean(JVMConfigurationKeys.SKIP_RUNTIME_VERSION_CHECK) && messageCollector != null) {
             JvmRuntimeVersionsConsistencyChecker.checkCompilerClasspathConsistency(
@@ -347,8 +347,12 @@ class KotlinCoreEnvironment private constructor(
         // TODO: add new Java modules to CliJavaModuleResolver
         val newRoots = classpathRootsResolver.convertClasspathRoots(contentRoots).roots
 
-        for (packagePartProvider in packagePartProviders) {
-            packagePartProvider.addRoots(newRoots, configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY))
+        if (packagePartProviders.isEmpty()) {
+            initialRoots.addAll(newRoots)
+        } else {
+            for (packagePartProvider in packagePartProviders) {
+                packagePartProvider.addRoots(newRoots, configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY))
+            }
         }
 
         return rootsIndex.addNewIndexForRoots(newRoots)?.let { newIndex ->