api: Enable IWYU in EmergeWithLintingEndpoint

This CL adds IWYU into EmergeWithLinting endpoint unless it is disabled.
Note that when this lands it will be disabled in the recipe so that we
can test this better using the led tool by first enabling with a recipe
change.

BUG=b:260476356
TEST=call scripts

Change-Id: I31301e1192956dc1f77ba5fb7f3e8cf432a4f0c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4059992
Reviewed-by: Christopher Di Bella <cjdb@google.com>
Tested-by: Ryan Beltran <ryanbeltran@chromium.org>
Commit-Queue: Ryan Beltran <ryanbeltran@chromium.org>
Reviewed-by: Tim Bain <tbain@google.com>
diff --git a/api/controller/toolchain.py b/api/controller/toolchain.py
index ccd2ddd..5c78247 100644
--- a/api/controller/toolchain.py
+++ b/api/controller/toolchain.py
@@ -419,9 +419,15 @@
     use_golint = (
         toolchain_pb2.LinterFinding.GO_LINT not in input_proto.disabled_linters
     )
+    use_iwyu = (
+        toolchain_pb2.LinterFinding.IWYU not in input_proto.disabled_linters
+    )
 
     findings = build_linter.emerge_with_linting(
-        use_clippy=use_clippy, use_tidy=use_tidy, use_golint=use_golint
+        use_clippy=use_clippy,
+        use_tidy=use_tidy,
+        use_golint=use_golint,
+        use_iwyu=use_iwyu,
     )
 
     for finding in findings: