Pass ldflags to the Dockerfile (#681)

<!-- Provide a brief summary of your changes -->

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following fixes an issue where the ldflags were not passed to the
Dockerfile, so the binary cannot populate its version-related variables
accordingly

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

Dockerfile

@@ -10,7 +10,14 @@ RUN go mod download
 COPY . .
 
 ARG GO_BUILD_TAGS
-RUN go build ${GO_BUILD_TAGS:+-tags="$GO_BUILD_TAGS"} -o /build/registry ./cmd/registry
+ARG VERSION=dev
+ARG GIT_COMMIT=unknown
+ARG BUILD_TIME=unknown
+
+RUN go build \
+    ${GO_BUILD_TAGS:+-tags="$GO_BUILD_TAGS"} \
+    -ldflags="-X main.Version=${VERSION} -X main.GitCommit=${GIT_COMMIT} -X main.BuildTime=${BUILD_TIME}" \
+    -o /build/registry ./cmd/registry
 
 FROM alpine:latest
 WORKDIR /app