Fix win-guest-agent-build-exe.bat
Fix win-guest-agent-build-exe.bat

File paths must use backslashes.

Change-Id: I24609f3afccd364ba2717e57cf241711f2461c91
Signed-off-by: Lev Veyde <32edd3ccb8e9d69e90ee9ce8dbc368c1f61bdf7b@redhat.com>

silenceli/oga-windows,oVirt/ovirt-guest-agent,silenceli/oga-windows,oVirt/ovirt-guest-agent,silenceli/oga-windows,silenceli/oga-windows,oVirt/ovirt-guest-agent,oVirt/ovirt-guest-agent