[build] Fix dart2js_compile action dependencies

Add dependency on unsound platform files.

This should fix the following flaky CQ failure:

    FAILED: dev_compiler/build/web/dart_stack_trace_mapper.js
    Error: Input file not found: dart2js_platform_unsound.dill.
    ...

Compilation action tries to read the unsound version of the platform,
but the GN template only specifies the dependency on the sound platform
making build non-hermetic.

Change-Id: If13431b1682e35a419cb6865c38e2b69348751f4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/221084
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Slava Egorov <vegorov@google.com>
diff --git a/utils/dartdevc/BUILD.gn b/utils/dartdevc/BUILD.gn
index da80743..5d93e80 100644
--- a/utils/dartdevc/BUILD.gn
+++ b/utils/dartdevc/BUILD.gn
@@ -49,11 +49,16 @@
   abs_output = rebase_path(out)
 
   prebuilt_dart_action(target_name) {
-    deps = invoker.deps + [ "../compiler:compile_dart2js_platform" ]
+    deps = invoker.deps + [
+             "../compiler:compile_dart2js_platform",
+             "../compiler:compile_dart2js_platform_unsound",
+           ]
 
     inputs = [
       "$root_out_dir/dart2js_platform.dill",
+      "$root_out_dir/dart2js_platform_unsound.dill",
       "$root_out_dir/dart2js_outline.dill",
+      "$root_out_dir/dart2js_outline_unsound.dill",
     ]
     outputs = [ out ]