Add support for building patched_sdk and platform.dill for dart2js:

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index c273be8460159720aecda58386bcd5956d73a098..e00290ae5c94523cd7306f5fc7ef3a75dfc0969f 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -107,12 +107,12 @@ class KernelTarget extends TargetImplementation {
   final TypeBuilder dynamicType =
       new KernelNamedTypeBuilder("dynamic", null, -1, null);
 
-  KernelTarget(
-      DillTarget dillTarget, TranslateUri uriTranslator, this.strongMode,
+  KernelTarget(DillTarget dillTarget, TranslateUri uriTranslator,
+      this.strongMode, bool forDart2js,
       [Map<String, Source> uriToSource])
       : dillTarget = dillTarget,
         uriToSource = uriToSource ?? CompilerContext.current.uriToSource,
-        super(dillTarget.ticker, uriTranslator) {
+        super(dillTarget.ticker, uriTranslator, forDart2js) {
     resetCrashReporting();
     loader = createLoader();
   }
@@ -270,10 +270,12 @@ class KernelTarget extends TargetImplementation {
       loader.finishStaticInvocations();
       finishAllConstructors();
       loader.finishNativeMethods();
-      transformMixinApplications();
-      // TODO(ahe): Don't call this from two different places.
-      setup_builtin_library.transformProgram(program);
-      otherTransformations();
+      if (forVm) {
+        transformMixinApplications();
+        // TODO(ahe): Don't call this from two different places.
+        setup_builtin_library.transformProgram(program);
+        otherTransformations();
+      }
       if (dumpIr) this.dumpIr();
       if (verify) this.verify();
       errors.addAll(loader.collectCompileTimeErrors().map((e) => e.format()));
@@ -388,7 +390,7 @@ class KernelTarget extends TargetImplementation {
         program.mainMethod = builder.procedure;
       }
     }
-    if (errors.isEmpty || dillTarget.isLoaded) {
+    if (forVm && (errors.isEmpty || dillTarget.isLoaded)) {
       setup_builtin_library.transformProgram(program);
     }
     ticker.logMs("Linked program");