dev.Dockerfile: allow forcing an lnd version

We can now use the `LND_VERSION` build argument to force a specific LND
version to be used when building. If the `LND_VERSION` build argument is
not set, then build continues as before this change and uses the version
already defined in `go.mod` and `go.sum`.

Author: ZZiigguurraatt

dev.Dockerfile

@@ -41,6 +41,11 @@ ARG NO_UI
 # Install dependencies and install/build lightning-terminal.
 RUN apk add --no-cache --update alpine-sdk make \
   && cd /go/src/github.com/lightninglabs/lightning-terminal \
+  # If a custom lnd version is supplied, force it now.
+  && if [ -n "$LND_VERSION" ]; then \
+    go get -v github.com/lightningnetwork/lnd@$LND_VERSION \
+    && go mod tidy; \
+  fi \
   # If a custom taproot-assets version is supplied, force it now.
   && if [ -n "$TAPROOT_ASSETS_VERSION" ]; then \
     go get -v github.com/lightninglabs/taproot-assets@$TAPROOT_ASSETS_VERSION \