Shale drillers are scrambling to raise cash as financing from Wall Street dries up. The companies behind the U.S. fracking boom are turning to asset sales, drilling partnerships and other alternative financing to supplement their cash flow. These forms of funding often come with higher interest rates or carry other downsides, such as giving outside investors a hefty share of future oil and gas production, but are gaining traction as drillers face dwindling access to traditional sources of capital. …