Don't put an MC/Forge source file in generated sources directory if a file of the same name exists in the main TT source directory.
Don't put an MC/Forge source file in generated sources directory if a file of the same name exists in the main TT source directory.

Signed-off-by: Ross Allan <ca2c77e14df1e7ee673215c1ef658354e220f471@gmail.com>

nallar/TickThreading