[Sourcemap] Extract addLink from SourceMap3Builder as a addSourceMappingURL

The general goal is remove dependency on TextOutput and
make it simpler to use for wasm backend.

js/js.sourcemap/src/org/jetbrains/kotlin/js/sourceMap/SourceMap3Builder.kt

@@ -6,7 +6,6 @@ package org.jetbrains.kotlin.js.sourceMap
 
 import gnu.trove.TObjectIntHashMap
 import org.jetbrains.kotlin.js.parser.sourcemaps.*
-import org.jetbrains.kotlin.js.util.TextOutput
 import java.io.File
 import java.io.IOException
 import java.io.Reader
@@ -192,12 +191,6 @@ class SourceMap3Builder(
         }
     }
 
-    override fun addLink() {
-        textOutput.print("\n//# sourceMappingURL=")
-        textOutput.print(generatedFile!!.name)
-        textOutput.print(".map\n")
-    }
-
     private object Base64VLQ {
         // A Base64 VLQ digit can represent 5 bits, so it is base-32.
         private const val VLQ_BASE_SHIFT = 5

js/js.sourcemap/src/org/jetbrains/kotlin/js/sourceMap/SourceMapBuilder.java

@@ -10,8 +10,6 @@ import java.io.File;
 public interface SourceMapBuilder extends SourceMapMappingConsumer {
     void skipLinesAtBeginning(int count);
 
-    void addLink();
-
     File getOutFile();
 
     String build();

js/js.sourcemap/src/org/jetbrains/kotlin/js/sourceMap/utils.kt

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2022 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.
+ */
+
+package org.jetbrains.kotlin.js.sourceMap
+
+import org.jetbrains.kotlin.js.util.TextOutput
+import java.io.File
+
+fun TextOutput.addSourceMappingURL(outputJsFile: File) {
+    print("\n//# sourceMappingURL=")
+    print(outputJsFile.name)
+    print(".map\n")
+}