Add precompiled cf_segments tool as x20 dependency

Since the golem builders do not have x20 access it will not be able to
compile CF segments. We therefore make a precompiled version and put
it as a depencency for the runners to use.

Change-Id: I55fbe9e02551fd51ef4e0145b4a4b0d3fb1c17a8
diff --git a/.gitignore b/.gitignore
index de74144..14e24ec 100644
--- a/.gitignore
+++ b/.gitignore
@@ -37,6 +37,8 @@
 third_party/benchmarks/santa-tracker.tar.gz
 third_party/classlib.tar.gz
 third_party/classlib
+third_party/cf_segments.tar.gz
+third_party/cf_segments
 third_party/chrome.tar.gz
 third_party/chrome
 third_party/dart-sdk