win-build: Fixes a kconfig incompatibility for Windows

In windows systems the rename() function fails if the new name
of the original file corresponds to a file that already exists.

The fix removes the new file before renaming the original one.

Jira: ZEP-980

Change-Id: Ib3a43db86c0dd3fabb592f53ea7619eb5738bb65
Signed-off-by: Juan Manuel Cruz <juan.m.cruz.alcaraz@intel.com>