[FIR] Support creation of IR of common + platform sources in FirAnalyzerFacade

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/analysis/FirAnalyzerFacade.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.fir.builder.PsiHandlingMode
 import org.jetbrains.kotlin.fir.builder.RawFirBuilder
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.lightTree.LightTree2Fir
+import org.jetbrains.kotlin.fir.moduleData
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.firProvider
 import org.jetbrains.kotlin.fir.resolve.providers.impl.FirProviderImpl
@@ -101,8 +102,13 @@ class FirAnalyzerFacade(
         if (_scopeSession == null) runResolution()
         val signaturer = JvmIdSignatureDescriptor(JvmDescriptorMangler(null))
 
+        val commonFirFiles = session.moduleData.dependsOnDependencies
+            .map { it.session }
+            .filter { it.kind == FirSession.Kind.Source }
+            .flatMap { (it.firProvider as FirProviderImpl).getAllFirFiles() }
+
         return Fir2IrConverter.createModuleFragment(
-            session, _scopeSession!!, firFiles!!,
+            session, _scopeSession!!, firFiles!! + commonFirFiles,
             languageVersionSettings, signaturer,
             extensions, FirJvmKotlinMangler(session), IrFactoryImpl,
             FirJvmVisibilityConverter,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirProviderImpl.kt

@@ -290,6 +290,10 @@ class FirProviderImpl(val session: FirSession, val kotlinScopeProvider: FirKotli
     override fun getClassNamesInPackage(fqName: FqName): Set<Name> {
         return state.classesInPackage[fqName] ?: emptySet()
     }
+
+    fun getAllFirFiles(): List<FirFile> {
+        return state.fileMap.values.flatten()
+    }
 }
 
 private const val rebuildIndex = true