Introduce check to see if a library was registered by a loadLibrary call.

Author: MichaelHaas99

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/c/NativeLibraries.java

@@ -501,6 +501,7 @@ public boolean isPotentialBuiltinJNILibrary(String library) {
 
     public void markPotentialBuiltinJNILibraryReachable(String library) {
         assert potentialBuiltinJNILibraryMap.containsKey(library);
+        VMError.guarantee(!potentialBuiltinJNILibraryMap.get(library).isReachable(), library);
         potentialBuiltinJNILibraryMap.get(library).markReachable();
     }