swift234

[cmake] Do not set CMAKE_INCLUDE_CURRENT_DIR.

Setting this value is equivalent to setting:

include_directories(${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})

in all subdirectories. Since these are all macros, this means that we are adding to the configuration
path the root swift directory. There is no reason to do this and will result in
confusion/bugs in the future.

rdar://26154980