Multistage cargo build for x86 and ARM

 - Conditionally `cargo build` for platforms of x86_64 or ARM.
 - In the final Docker stage we copy the built binary to alpine, and run with environment:
 - $LND_HOST, $LND_GRPC_PORT, $TLS_FILE, $MACAROON_FILE"

Dockerfile

@@ -1,23 +1,51 @@
-# Build Stage 
-# nightly-slim?
-FROM rustlang/rust:nightly AS builder
-RUN rustup target add x86_64-unknown-linux-musl
-RUN apt -y update
-RUN apt install -y musl-tools musl-dev
+# Multistage Build for Loin (x86_64 or ARM)
+#
+# Conditionally `cargo build` for platforms of x86_64 or ARM.
+# In the final Docker stage we copy the built binary to alpine, and run with environment:
+# $LND_HOST, $LND_GRPC_PORT, $TLS_FILE, $MACAROON_FILE"
 
+# Initial build Stage 
+# use nightly-slim?
+FROM rustlang/rust:nightly AS builder
+ARG TARGETARCH
+ENV RUSTFLAGS="-Z macro-backtrace"
+ENV RUST_BACKTRACE=1
 WORKDIR /usr/src/loin
 COPY Cargo.toml Cargo.lock build.rs config_spec.toml ./
 COPY src ./src
 COPY static ./static
 COPY node_modules ./node_modules
-ENV RUSTFLAGS="-Z macro-backtrace"
-ENV RUST_BACKTRACE=1
+
+# x86_64
+FROM builder AS branch-version-amd64
+RUN apt-get update && apt-get install -y musl-tools musl-dev
+RUN echo "Building x86_64 (${TARGETARCH})"
+RUN rustup target add x86_64-unknown-linux-musl
 RUN cargo install --features=test_paths --target x86_64-unknown-linux-musl --path .
+p
+# ARM
+FROM builder AS branch-version-arm64
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    g++-arm-linux-gnueabihf \
+    libc6-dev-armhf-cross
+RUN echo "Building arm (${TARGETARCH})"
+RUN rustup target add armv7-unknown-linux-gnueabihf
+ENV CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER=arm-linux-gnueabihf-gcc \
+    CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_RUNNER="/linux-runner armv7hf" \
+    CC_armv7_unknown_linux_gnueabihf=arm-linux-gnueabihf-gcc \
+    CXX_armv7_unknown_linux_gnueabihf=arm-linux-gnueabihf-g++ \
+    BINDGEN_EXTRA_CLANG_ARGS_armv7_unknown_linux_gnueabihf="--sysroot=/usr/arm-linux-gnueabihf" \
+    QEMU_LD_PREFIX=/usr/arm-linux-gnueabihf \
+    RUST_TEST_THREADS=1 \
+    PKG_CONFIG_PATH="/usr/lib/arm-linux-gnueabihf/pkgconfig/:${PKG_CONFIG_PATH}"
+RUN cargo install --features=test_paths --target armv7-unknown-linux-gnueabihf --path .
 
-# Bundle Stage
+# We want to build for either x86_64 or ARM using the above options and docker var TARGETARCH
+FROM branch-version-${TARGETARCH} AS chosen_builder
+RUN echo "Called build!"
+
+# Run loin
 FROM alpine
-COPY --from=builder /usr/local/cargo/bin/loin /home/ 
-COPY loin.conf /home/
+COPY --from=chosen_builder /usr/local/cargo/bin/loin /home/ 
 USER 1000
-CMD ["/home/loin", "--conf", "/home/loin.conf"]]
-
+CMD ["/home/loin", "--bind_port", "4444", "--lnd_address=$LND_HOST:$LND_GRPC_PORT", "--lnd_cert_path=$TLS_FILE", "--lnd_macaroon_path=$MACAROON_FILE"]