Update ftl-build container to v3.21

DL6ER · DL6ER · commit 6f70cd545f63 · 2024-12-09T09:52:58.000+01:00
Signed-off-by: DL6ER &lt;dl6er@dl6er.de&gt;
diff --git a/ftl-build/Dockerfile b/ftl-build/Dockerfile
@@ -1,4 +1,4 @@
-ARG CONTAINER="alpine:latest"
+ARG CONTAINER="alpine:3.21"
 FROM ${CONTAINER} AS builder
 
 ARG TARGETPLATFORM
