fixup! Ensure method in interpreter root is unique.

Author: gilles-duboscq

substratevm/src/com.oracle.svm.interpreter/src/com/oracle/svm/interpreter/InterpreterFeature.java

@@ -227,7 +227,9 @@ public void beforeAnalysis(BeforeAnalysisAccess access) {
 
     private static AnalysisMethod getUniqueMethod(Class<?> cls, FeatureImpl.BeforeAnalysisAccessImpl accessImpl) {
         AnalysisMethod[] declaredMethods = accessImpl.getMetaAccess().lookupJavaType(cls).getDeclaredMethods(false);
-        VMError.guarantee(declaredMethods.length == 1, "Expected exactly one method in " + cls + ", found: " + Arrays.toString(declaredMethods));
+        if (declaredMethods.length != 1) {
+            throw VMError.shouldNotReachHere("Expected exactly one method in " + cls + ", found: " + Arrays.toString(declaredMethods));
+        }
         return declaredMethods[0];
     }