Build: Convert windows paths to unix paths

Replace all "\" with "/" in path names to keep #include lines
consistent, whether the files were generated on windows or linux.

Signed-off-by: TTornblom <thomas.tornblom@iar.com>
Change-Id: Iae59f91515056e8318a247a681a5cd7118749660
diff --git a/tools/tfm_parse_manifest_list.py b/tools/tfm_parse_manifest_list.py
index 9805cc5..319e48b 100644
--- a/tools/tfm_parse_manifest_list.py
+++ b/tools/tfm_parse_manifest_list.py
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2018-2019, Arm Limited. All rights reserved.
+# Copyright (c) 2018-2020, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -105,7 +105,7 @@
         manifest_dir, manifest_name = os.path.split(manifest_path)
         outfile_name = manifest_name.replace('yaml', 'h').replace('json', 'h')
         context['file_name'] = outfile_name.replace('.h', '')
-        outfile_name = os.path.join(manifest_dir, "psa_manifest", outfile_name)
+        outfile_name = os.path.join(manifest_dir, "psa_manifest", outfile_name).replace('\\', '/')
 
         manifest_header_list.append(outfile_name)