Add RBE_num_local_reruns and RBE_num_remote_reruns environment variables
to enable reruns in RBE.

Change-Id: I668ad78027cd0756d5e0bf2f788667b47175785f
diff --git a/ui/build/ninja.go b/ui/build/ninja.go
index 5961c45..41de6bd 100644
--- a/ui/build/ninja.go
+++ b/ui/build/ninja.go
@@ -141,6 +141,8 @@
 
 			// RBE client
 			"RBE_compare",
+			"RBE_num_local_reruns",
+			"RBE_num_remote_reruns",
 			"RBE_exec_root",
 			"RBE_exec_strategy",
 			"RBE_invocation_id",