Avoid the macOS case-insensitive app/CLI build collision

scripts/build-desktop-app.sh

@@ -16,11 +16,11 @@ if [ ! -x "$FYNE" ]; then
   FYNE="$(go env GOPATH)/bin/fyne"
 fi
 
-mkdir -p .local
-go build -o .local/Tunnel -ldflags "-X main.version=$VERSION" ./cmd/tunnel-desktop
+mkdir -p .local/desktop
+go build -o .local/desktop/Tunnel -ldflags "-X main.version=$VERSION" ./cmd/tunnel-desktop
 rm -rf Tunnel.app
 "$FYNE" package -os darwin \
-  -executable .local/Tunnel \
+  -executable .local/desktop/Tunnel \
   -name Tunnel -app-id dev.tzgyn.tunnel \
   -app-version "$VERSION" -app-build "$BUILD" \
   -icon assets/icon.png -release