Xcode: Restore Swift framework search directories

Previously we selected a single "language for preprocessor" with which
to compute both target-wide `GCC_PREPROCESSOR_DEFINITIONS` and
`{HEADER,FRAMEWORK}_SEARCH_PATHS`.  Since commit c0dd3dd2c1 (Xcode:
Evaluate Swift compile definitions separately, 2022-10-25,
v3.25.0-rc3~16^2) we never compute `GCC_PREPROCESSOR_DEFINITIONS` for
Swift.  Therefore we need to select the language for target-wide include
and framework directories separately.

Fixes: #24116