Cleanup: CMake: Modernize bf_extern_curve_fit_nd dependencies

Pretty straightforward

- Remove any curve_fit_nd paths from INC
- Add a dependency though LIB when missing

context: https://devtalk.blender.org/t/cmake-cleanup/30260

Pull Request: https://projects.blender.org/blender/blender/pulls/110762

extern/curve_fit_nd/CMakeLists.txt

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 set(INC
-  .
+  PUBLIC .
 )
 
 set(INC_SYS
@@ -26,3 +26,4 @@ set(LIB
 )
 
 blender_add_lib(extern_curve_fit_nd "${SRC}" "${INC}" "${INC_SYS}" "${LIB}")
+add_library(bf::extern::curve_fit_nd ALIAS extern_curve_fit_nd)

source/blender/blenkernel/CMakeLists.txt

@@ -32,7 +32,6 @@ set(INC
   ../../../intern/memutil
   ../../../intern/mikktspace
   ../../../intern/opensubdiv
-  ../../../extern/curve_fit_nd
   ../../../extern/fmtlib/include
 
   # RNA_prototypes.h
@@ -542,6 +541,7 @@ set(LIB
   bf_depsgraph
   PRIVATE bf::dna
   bf_draw
+  PRIVATE bf::extern::curve_fit_nd
   bf_functions
   bf_gpencil_modifiers_legacy
   bf_gpu

source/blender/editors/curve/CMakeLists.txt

@@ -11,7 +11,6 @@ set(INC
   ../../makesrna
   ../../windowmanager
   ../../../../intern/clog
-  ../../../../extern/curve_fit_nd
   # RNA_prototypes.h
   ${CMAKE_BINARY_DIR}/source/blender/makesrna
 )
@@ -38,6 +37,7 @@ set(LIB
   bf_blenkernel
   PRIVATE bf::blenlib
   PRIVATE bf::dna
+  PRIVATE bf::extern::curve_fit_nd
   PRIVATE bf::intern::guardedalloc
   extern_curve_fit_nd
 )