ENH: Update CastXML command to use --castxml-output=1

Remove reliance on the "--castxml-gccxml" that does not support newer
compilers.

For example:
LLVM PR 114788 switched libc++'s <cstddef> to use decltype() to define
size_t. Any build using libc++ 21 or later will have this problem, not
just those that get it via the macOS SDK.

Author: hjmjohnson

Wrapping/Generators/SwigInterface/igenerator.py

@@ -1948,7 +1948,10 @@ def main():
     pygccxml.declarations.scopedef_t.ALLOW_EMPTY_MDECL_WRAPPER = True
 
     pygccxml_config = pygccxml.parser.config.xml_generator_configuration_t(
-        xml_generator_path=options.castxml_path, xml_generator="castxml"
+        xml_generator_path=options.castxml_path,
+        xml_generator="castxml",
+        # Use castxml-output=1 to take advantage of the newer XML format
+        flags=["--castxml-output=1"],
     )
 
     submodule_names_list: list[str] = []

Wrapping/macro_files/itk_auto_load_submodules.cmake

@@ -205,7 +205,7 @@ function(generate_castxml_commandline_flags)
       ${xml_file}
     COMMAND
       ${_build_env} ${_ccache_cmd} ${CASTXML_EXECUTABLE} -o ${xml_file}
-      --castxml-gccxml ${_target} --castxml-start _wrapping_ ${_castxml_cc} -w
+      --castxml-output=1 ${_target} --castxml-start _wrapping_ ${_castxml_cc} -w
       -c # needed for ccache to think we are not calling for link
       @${castxml_inc_file} ${cxx_file}
     VERBATIM