chore(Dockerfile): switch to alpine for building the binary

Currently the SLE BCI doesn't provide go 1.26.4, which results in a
failure.

Consume the Go compiler from the official Go container image.

Signed-off-by: Flavio Castelli <fcastelli@suse.com>

Author: flavio

package/Dockerfile

@@ -5,7 +5,7 @@ FROM registry.suse.com/bci/bci-busybox:${BCI_VERSION} AS final
 # Image that provides cross compilation tooling.
 FROM --platform=$BUILDPLATFORM rancher/mirrored-tonistiigi-xx:1.3.0 AS xx
 
-FROM --platform=$BUILDPLATFORM registry.suse.com/bci/golang:1.26 AS build
+FROM --platform=$BUILDPLATFORM golang:1.26-alpine AS build
 
 ARG TARGETPLATFORM
 ARG PROJECT_PATH