I am still having this problem.
I have cleared the gradle cache, deleted the forge install folder, deleted the .gradle folder in ~ and it's still failing with the following errors every time during the doForgePatches sequence:
Patching failed: net/minecraft/client/renderer/RenderBlocks.java Cannot find hunk target
Hunk 6 failed! Cannot find hunk target
Hunk 10 failed! Cannot find hunk target
Patching failed: net/minecraft/client/renderer/entity/RenderItem.java Cannot find hunk target
Hunk 11 failed! Cannot find hunk target
Hunk 12 failed! Cannot find hunk target
Any help at all would be appreciated. Thank you.