swift234

[AddSwift.cmake] Remove leftover use_internal_sdk parameter values

The `use_internal_sdk` flag has been removed from `_add_variant_link_flags` and
`_add_variant_c_compile_flags` in commit
d9bbb6caf09a512f10edc4379194ec6a07aed847

In four instances where previously FALSE was given as the value for that
parameter, this value has not been removed from the call.
This causes the two functions to try to append flags to FALSE instead of the
respective link_flags and c_compile_flags variables.