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

runtime/vm/BUILD.gn

Index: runtime/vm/BUILD.gn
diff --git a/runtime/vm/BUILD.gn b/runtime/vm/BUILD.gn
index b0f9c7fcf383a4a34e75cf4ef23c68ad2b7f332a..2a2534d793f59462d33b89a973aa3303a62970fd 100644
--- a/runtime/vm/BUILD.gn
+++ b/runtime/vm/BUILD.gn
@@ -4,7 +4,6 @@
 
 import("../../build/executable_suffix.gni")
 import("../../build/prebuilt_dart_sdk.gni")
-import("../../utils/generate_patch_sdk.gni")
 import("gypi_contents.gni")
 import("../runtime_args.gni")
 
@@ -382,7 +381,7 @@ template("concatenate_patch") {
   }
 }
 
-template("generate_vm_patched_sdk") {
+template("generate_patched_sdk") {
   assert(defined(invoker.libraries), "Need libraries in $target_name")
 
   concatenation_target_names = []
@@ -401,15 +400,51 @@ template("generate_vm_patched_sdk") {
 
   # Build the patched sdk out of the concatenated patches and the special
   # libraries.
-  generate_patched_sdk(target_name) {
-    mode = "vm"
+  action(target_name) {
     deps = concatenation_target_names
-    input_patches_dir = "$target_gen_dir/patches"
-    patched_sdk_dir = "patched_sdk"
+    if (!prebuilt_dart_exe_works) {
+      deps += [ "../bin:dart_bootstrap($host_toolchain)" ]
+    }
+
+    patches_dir = "$target_gen_dir/patches"
+    patched_sdk_dir = "$root_out_dir/patched_sdk"
+
+    script = "../../tools/patch_sdk.py"
+
+    # We list the `patch_sdk.dart` tool here because the [script] (which is
+    # implicitly an input) will call it.
+    inputs = [
+      "../../tools/patch_sdk.dart",
+    ]
+    depfile = "$root_out_dir/patched_sdk.d"
+
+    outputs = [
+      # Instead of listing all outputs we list a single well-known one.
+      "${patched_sdk_dir}/platform.dill",
+    ]
+
+    args = [ "--quiet" ]
+    if (!prebuilt_dart_exe_works) {
+      dart_out_dir = get_label_info("../bin:dart_bootstrap($host_toolchain)",
+                                    "root_out_dir")
+      dart_bootstrap =
+          rebase_path("$dart_out_dir/dart_bootstrap$executable_suffix")
+      args += [
+        "--dart-executable",
+        dart_bootstrap,
+      ]
+    }
+    args += [
+      "vm",
+      rebase_path("../../sdk"),
+      rebase_path(patches_dir, root_build_dir),
+      rebase_path(patched_sdk_dir, root_build_dir),
+      rebase_path("../../.packages"),
+    ]
   }
 }
 
-generate_vm_patched_sdk("patched_sdk") {
+generate_patched_sdk("patched_sdk") {
   libraries = [
     [
       "async",