[infra-ish] Fix compile_flutter.sh after flutter engine was merged into flutter/flutter

This should fix the current failures on the flutter-frontend bot.

Change-Id: I26268a002055aca2eb46af74003b6c30df3efed9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/404101
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Jens Johansen <jensj@google.com>

tools/bots/flutter/compile_flutter.sh

diff --git a/tools/bots/flutter/compile_flutter.sh b/tools/bots/flutter/compile_flutter.sh
index 045c82c..fb2d6bc 100755
--- a/tools/bots/flutter/compile_flutter.sh
+++ b/tools/bots/flutter/compile_flutter.sh
@@ -59,24 +59,17 @@
 pushd flutter
 bin/flutter config --no-analytics
 bin/flutter update-packages
-popd  # flutter
-
-# Directly in temp directory again.
-git clone --single-branch --depth=1 -vv \
-    https://dart.googlesource.com/external/github.com/flutter/buildroot src
-pushd src
-git clone --single-branch --branch main --depth=1 -vv \
-    https://dart.googlesource.com/external/github.com/flutter/engine flutter
-pushd flutter
-mkdir -p third_party
-pushd third_party
+pushd engine
+pushd src/flutter/third_party
 ln -s $checkout dart
-popd  # third_party
-popd  # flutter
-popd  # src
+popd  # src/flutter/third_party
 
+# This script doesn't seem to work anymore.
 ./src/flutter/third_party/dart/tools/patches/flutter-engine/apply.sh || true
 
+popd  # engine
+popd  # flutter
+
 mkdir flutter_patched_sdk
 
 $checkout/tools/sdks/dart-sdk/bin/dart \
@@ -100,7 +93,7 @@
     --target=flutter \
     dart:core \
     --single-root-scheme=org-dartlang-sdk \
-    --single-root-base=src \
+    --single-root-base=flutter/engine/src \
     org-dartlang-sdk:///flutter/lib/snapshot/libraries.json \
     vm_outline_strong.dill \
     flutter_patched_sdk/platform_strong.dill \