[IR] Use separate directories for each module for IR dumps

It allows avoiding overwriting content generated for other modules.

Also, added using additional ".kt" prefix to file extension for dumps generated with  Kotlin like syntax.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/phaser/DumperVerifier.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -87,7 +87,7 @@ fun dumpIrElement(actionState: ActionState, data: IrElement, @Suppress("UNUSED_P
         dumpText = data.dump()
     }
 
-    val title = "-- IR for $elementName $beforeOrAfterStr ${actionState.phase.description}\n"
+    val title = "// --- IR for $elementName $beforeOrAfterStr ${actionState.phase.description}\n"
     return title + dumpText
 }
 
@@ -101,7 +101,11 @@ fun <Data, Context> dumpToFile(
         val directoryPath = actionState.config.dumpToDirectory ?: return
         val dumpContent = dumper(actionState, data, context) ?: return
 
-        val directoryFile = File(directoryPath)
+        // TODO in JVM BE most of lowerings run per file and "dump" is called per file,
+        //  so each run of this function overwrites dump written for the previous one.
+        val directoryFile =
+            File(directoryPath +
+                         ((data as? IrModuleFragment)?.let { "/" + it.name.asString().removeSurrounding("<", ">") } ?: ""))
         if (!directoryFile.isDirectory)
             if (!directoryFile.mkdirs())
                 error("Can't create directory for IR dumps at $directoryPath")
@@ -109,7 +113,10 @@ fun <Data, Context> dumpToFile(
         // Make dump files in a directory sorted by ID
         val phaseIdFormatted = "%02d".format(actionState.phaseCount)
 
-        val fileName = "${phaseIdFormatted}_${actionState.phase.name}.$fileExtension"
+        val dumpStrategy = System.getProperty("org.jetbrains.kotlin.compiler.ir.dump.strategy")
+        val extPrefix = if (dumpStrategy == "KotlinLike") "kt." else ""
+
+        val fileName = "${phaseIdFormatted}_${actionState.phase.name}.$extPrefix$fileExtension"
 
         File(directoryFile, fileName).writeText(dumpContent)
     }