Add hdctools to manifest

hdctools changed their default branch from master to main. git-2.eclass
assumes master to be the default branch, so lets download this repo
explicitly.

BUG=None
TEST=repo init, repo sync, cros_sdk --nouse-image
RELEASE_NOTE=None

Change-Id: Ia21b80101723c8acb61f915dd2921fc61c4b0c33
Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/11050
Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
diff --git a/flaky_repos.xml b/flaky_repos.xml
index 204d2be..05814c2 100644
--- a/flaky_repos.xml
+++ b/flaky_repos.xml
@@ -46,6 +46,10 @@
   <project path="src/platform/microbenchmarks"
            name="chromiumos/platform/microbenchmarks"
            remote="chromium" />
+  <project path="src/third_party/hdctools"
+           name="chromiumos/third_party/hdctools"
+           revision="refs/heads/main"
+           remote="chromium" />
 
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    breakpad and lss are special; they need to be pinned to specific commit