Heat oil in saucepan and saute onions for 4 minutes. Add jalapenos and cumin seeds and saute until fragrant. Add the cloves, cinnamon, and coriander. When fragrant, add the mangoes. Bring to a boil, reduce to simmer and cook until mangoes are soft. Add the lime juice, rice wine vinegar, 1/4 cup vegetable oil, minced ginger, and Demerara sugar and bring back to a boil. Reduce heat and simmer for 1 hour, stirring occasionally until chutney is thick. Pour into hot and sterilized jars and seal when cold.