Make hayabusa/takajo versions build ARGs so the buildbot can bump them

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Dockerfile

@@ -3,8 +3,9 @@ FROM alpine AS builder
 
 # Get the target platform
 ARG TARGETPLATFORM
-ENV HAYABUSA_VERSION=3.8.1
-ENV TAKAJO_VERSION=2.15.1
+# Build args so the buildbot can inject the latest release without a commit.
+ARG HAYABUSA_VERSION=3.8.1
+ARG TAKAJO_VERSION=2.15.1
 
 # Install necessary tools
 RUN apk add --no-cache unzip wget git