scripts: build: parse_syscalls: Fix duplicate paths on windows

Fixes an issue on windows where there would be many permutations
of paths with different folder separators by converting to
posix-style path separators.

Issue was introduced by
https://github.com/zephyrproject-rtos/zephyr/pull/58351

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

scripts/build/parse_syscalls.py

@@ -29,6 +29,7 @@ import re
 import argparse
 import os
 import json
+from pathlib import PurePath
 
 regex_flags = re.MULTILINE | re.VERBOSE
 
@@ -101,6 +102,8 @@ def analyze_headers(include_dir, scan_dir, file_list):
                                                    'common.h'))):
                     continue
 
+                path = PurePath(os.path.normpath(path)).as_posix()
+
                 if path not in syscall_files:
                     if include_dir and base_path in include_dir:
                         syscall_files[path] = {"emit" : True}