facilitator: build rust:1.50.0-alpine3.13

Our NCI colleagues believe that this specific Alpine base image should
not exhibit the `musl` DNS issue. We will see!

facilitator/Dockerfile

@@ -1,4 +1,11 @@
-FROM rust:1.50 as builder
+FROM rust:1.50.0-alpine3.13 as builder
+
+RUN apk add libc-dev openssl-dev && apk update
+
+# This is required so OpenSSL links properly. OpenSSL is required by reqwest, as used by
+# prometheus with the `push` option.
+# https://users.rust-lang.org/t/sigsegv-with-program-linked-against-openssl-in-an-alpine-container/52172
+ENV RUSTFLAGS='-C target-feature=-crt-static'
 
 # Attempt to install a nonexistent package. This triggers
 # updating the crates.io index separately from building the
@@ -28,6 +35,7 @@ COPY ./avro-schema ./avro-schema
 COPY ./facilitator ./facilitator
 
 ARG BUILD_INFO=unspecified
+ENV OPENSSL_STATIC=true
 
 # This cargo build command must match the one above, or the build cache will not be reused.
 RUN cargo build --manifest-path ./facilitator/Cargo.toml