Re-add go:build ignore lines

This reverts commit bab2f96e2637acb107fe9b099c58befbca918748. This
clears the sea of red in my editor.

Change-Id: I600ef6c36556fb526da729f0f0d8bc69db5c5a08
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/59186
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/util/fetch_ech_config_list.go b/util/fetch_ech_config_list.go
index 8f09e66..732d0d3 100644
--- a/util/fetch_ech_config_list.go
+++ b/util/fetch_ech_config_list.go
@@ -12,6 +12,8 @@
 // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
+//go:build ignore
+
 package main
 
 import (