Build non-nullable or legacy SDK summary.

Bug: https://github.com/dart-lang/sdk/issues/38666
Change-Id: I24f6f36b5ed1dbef64588dd787aaf2abbd62f53c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/132800
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

utils/dartanalyzer/BUILD.gn

@@ -46,9 +46,17 @@ prebuilt_dart_action("generate_summary_strong") {
   outputs = [
     output,
   ]
-  args = [
-    "build-strong",
-    rebase_path(output),
-    rebase_path("../../sdk"),
-  ]
+  if (use_nnbd) {
+    args = [
+      "build-non-nullable",
+      rebase_path(output),
+      rebase_path("../../sdk_nnbd"),
+    ]
+  } else {
+    args = [
+      "build-legacy",
+      rebase_path(output),
+      rebase_path("../../sdk"),
+    ]
+  }
 }