Add user to Containerfile + configure user

Containerfile

@@ -1,6 +1,15 @@
 FROM docker.io/alpine:edge
+
 RUN apk add --no-cache buildah
 
+RUN 	adduser build; \
+	echo "build:100000:65536" | tee /etc/subuid > /etc/subgid; \
+	mkdir -p /home/build/.local/share/containers; \
+	chown -R build:build /home/build
 
-# Use chroot isolation to avoid unshare call
+# Use chroot isolation
 ENV BUILDAH_ISOLATION=chroot
+
+USER build
+WORKDIR /home/build
+