RIYADH, Jan 6 (Reuters) - Saudi Arabia&aposs Jabal Omar Development Company 4250.SE has secured a 4 billion riyal ($1.07 billion) loan to refinance part of an existing facility it signed in 2012 to fund its real estate project in Mecca, it said on Tuesday.Saudi Arabia&aposs largest listed developer by market value said the new loan from National Commercial Bank 1180.SE , to fund the project&aposs