Prevent initializing same system property to different values

Author: olpaw

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/SystemPropertiesSupport.java

@@ -40,6 +40,7 @@
 
 import com.oracle.svm.core.VM;
 import com.oracle.svm.core.config.ConfigurationValues;
+import com.oracle.svm.core.util.UserError;
 import com.oracle.svm.core.util.VMError;
 
 /**
@@ -202,7 +203,10 @@ public void setProperties(Properties props) {
      */
     @Override
     public void initializeProperty(String key, String value) {
-        savedProperties.put(key, value);
+        String prevValue = savedProperties.put(key, value);
+        if (prevValue != null && prevValue != value) {
+            UserError.abort("System property %s is initialized to %s but was previously initialized to %s.", key, value, prevValue);
+        }
         properties.setProperty(key, value);
     }