refactor: avoid specifying --platform in build.sh

Build only for default platform by default, if a custom platform is
required, users should pass `--platform` flag to the script.

build.sh

@@ -2,6 +2,6 @@
 set -a
 
 . ./deps.list
-docker buildx build --platform linux/amd64,linux/arm64 \
+docker buildx build \
     $(for v in $(cut -d '=' -f 1 < deps.list); do printf "%s " "--build-arg $v=$(printenv ${v})"; done) \
     ${@} .