validator_ragel: Link into TCB, use under env var

src/trusted/service_runtime/sel_main.c

Index: src/trusted/service_runtime/sel_main.c
diff --git a/src/trusted/service_runtime/sel_main.c b/src/trusted/service_runtime/sel_main.c
index 006c63c358aa82d775420e7b1ad6391932ba1f9c..78ed14a120578e37c224154f2e5c2c0eb476781c 100644
--- a/src/trusted/service_runtime/sel_main.c
+++ b/src/trusted/service_runtime/sel_main.c
@@ -544,6 +544,12 @@ int main(int  argc,
     }
   }
 
+  nap->enable_dfa_validator = 0;
+  if (getenv("NACL_DANGEROUS_USE_DFA_VALIDATOR") != NULL) {
+    fprintf(stderr, "DANGER! USING THE UNSTABLE DFA VALIDATOR!\n");
+    nap->enable_dfa_validator = 1;
+  }
+
   /* Sanity check. */
   NaClSignalAssertNoHandlers();