[tests] add PLUGIN directive following !3153

tests/misc/oracle/ulevel.res.oracle

@@ -4,8 +4,8 @@
 [eva] Initial state computed
 [eva:initial-state] Values of globals at initialization
   
+[eva] tests/misc/ulevel.i:13: starting to merge loop iterations
 [eva] tests/misc/ulevel.i:12: starting to merge loop iterations
-[eva] tests/misc/ulevel.i:11: starting to merge loop iterations
 [eva] done for function main
 [eva] ====== VALUES COMPUTED ======
 [eva:final-states] Values at end of function main:

tests/misc/ulevel.i

 /* run.config
-   OPT: -then -ulevel-force -eva
+  PLUGIN: @EVA_PLUGINS@
+  OPT: -then -ulevel-force -eva
  */
 
 /* Tests the syntaxic loop unrolling when triggered by an option change