COMP: Ensure full path ID for macOS libraries installed for fix-up

This commit resolves an issue in Slicer's fix-up process, specifically when
updating the installed executable and plugins using `@rpath`. To align with
this process, both the installed libraries and their dependent libraries must
have a full path. Consequently, we consistently clear `CMAKE_INSTALL_NAME_TOOL`
in all external projects. This adjustment is crucial due to the lack of an
explicit option in CMake to skip the "install_name_tool" call unless the variable
is cleared. Please refer to `cmInstallTargetGenerator::AddInstallNamePatchRule`
C++ function found in the CMake source code for a comprehensive understanding.

For historical context, the forceful setting of `CMAKE_INSTALL_NAME_TOOL` to an
empty value was originally introduced in commit 4c441a2 ("COMP: Fix MacOSX
packaging fixup associated with loadable module", 2012-10-25). Subsequently, the
comment "XXX Probably not needed anymore" was added in commit d276165 ("BUG:
Extension packaging: Ensure @rpath is not applied at build time", 2016-06-10) and
is now removed, as forcing the value is indispensable to support packaging of
external projects like VTK modules built externally.

CMake/SlicerCPack.cmake

@@ -168,8 +168,6 @@ else()
   #------------------------------------------------------------------------------
   # macOS specific configuration used by the "fix-up" script
   #------------------------------------------------------------------------------
-  set(CMAKE_INSTALL_NAME_TOOL "" CACHE FILEPATH "" FORCE)
-
   if(Slicer_USE_PYTHONQT)
     include(${Slicer_CMAKE_DIR}/SlicerBlockInstallExternalPythonModules.cmake)
   endif()

CMake/UseSlicer.cmake.in

@@ -302,7 +302,10 @@ endif()
 set(Slicer_BUNDLE_EXTENSIONS_LOCATION "")
 if(APPLE)
   set(Slicer_BUNDLE_EXTENSIONS_LOCATION "${Slicer_EXTENSIONS_DIRBASENAME}-${Slicer_REVISION}/${EXTENSION_NAME}/")
-  set(CMAKE_INSTALL_NAME_TOOL "" CACHE FILEPATH "" FORCE) # XXX Probably not needed anymore
+
+  set(CMAKE_INSTALL_NAME_TOOL "" CACHE FILEPATH "" FORCE)
+  mark_as_superbuild(VARS CMAKE_INSTALL_NAME_TOOL:FILEPATH ALL_PROJECTS)
+
   set(CMAKE_MACOSX_RPATH 0 CACHE BOOL "" FORCE)
   mark_as_superbuild(VARS CMAKE_MACOSX_RPATH:BOOL ALL_PROJECTS)
 endif()

CMakeLists.txt

@@ -66,6 +66,9 @@ if(APPLE)
     ALL_PROJECTS
     )
 
+  set(CMAKE_INSTALL_NAME_TOOL "" CACHE FILEPATH "" FORCE)
+  mark_as_superbuild(VARS CMAKE_INSTALL_NAME_TOOL:FILEPATH ALL_PROJECTS)
+
   set(CMAKE_MACOSX_RPATH 0)
   mark_as_superbuild(VARS CMAKE_MACOSX_RPATH:BOOL ALL_PROJECTS)
 endif()