swc-windows-installer.py: Add nesting setup/windows-installer/

Mimic the path that submodule users will have.

diff --git a/setup/swc-windows-installer.py b/setup/windows-installer/swc-windows-installer.py
similarity index 100%
rename from setup/swc-windows-installer.py
rename to setup/windows-installer/swc-windows-installer.py