Try to fix windows

Author: staticfloat

test/sandbox.jl

@@ -105,10 +105,16 @@ end
                     scent = "shadowed"
                 """)
             end
+
+            # Use `/` on windows as well
+            spp_path = joinpath(tmp, "Sandbox_PreservePreferences")
+            if Sys.iswindows()
+                spp_path = join(splitpath(spp_path), "/")
+            end
             open(joinpath(outer_layer, "Manifest.toml"), write=true) do io
                 println(io, """
                 [[Sandbox_PreservePreferences]]
-                path = "$(joinpath(tmp, "Sandbox_PreservePreferences"))"
+                path = "$(spp_path)"
                 uuid = "$(spp_uuid)"
                 """)
             end