Dockerfile: use more recent build env,
Thanks flucrezia for the suggestion
Closes:
-FROM alpine:3.10 AS builder
+FROM alpine:3.15 AS builder
ADD . /opt/carbon-c-relay-build
WORKDIR /opt/carbon-c-relay-build
@@ -7,7 +7,7 @@ RUN \
apk add --no-cache git bc build-base curl automake autoconf libtool && \
./configure && make
-FROM alpine:3.10
+FROM alpine:3.15
MAINTAINER Fabian Groffen
