Add dockerfile for aarch64 (arm64)

Dockerfile.aarch64

+# Using multistage build: 
+# 	https://docs.docker.com/develop/develop-images/multistage-build/
+# 	https://whitfin.io/speeding-up-rust-docker-builds/
+####################### VAULT BUILD IMAGE  #######################
+FROM node:8-alpine as vault
+
+ENV VAULT_VERSION "v2.3.0"
+
+ENV URL "https://github.com/bitwarden/web.git"
+
+RUN apk add --update-cache --upgrade \
+    curl \
+    git \
+    tar
+
+RUN git clone -b $VAULT_VERSION --depth 1 $URL web-build
+WORKDIR /web-build
+
+COPY /docker/set-vault-baseurl.patch /web-build/    
+RUN git apply set-vault-baseurl.patch
+
+RUN npm run sub:init && npm install
+
+RUN npm run dist \
+    && mv build /web-vault
+
+########################## BUILD IMAGE  ##########################
+# We need to use the Rust build image, because
+# we need the Rust compiler and Cargo tooling
+FROM rust as build
+
+RUN apt-get update \
+    && apt-get install -y \
+        gcc-aarch64-linux-gnu \
+    && mkdir -p ~/.cargo \
+    && echo '[target.aarch64-unknown-linux-gnu]' >> ~/.cargo/config \
+    && echo 'linker = "aarch64-linux-gnu-gcc"' >> ~/.cargo/config
+
+ENV CARGO_HOME "/root/.cargo"
+ENV USER "root"
+
+# Creates a dummy project used to grab dependencies
+RUN USER=root cargo new --bin app
+WORKDIR /app
+
+# Copies over *only* your manifests and vendored dependencies
+COPY ./Cargo.* ./
+COPY ./libs ./libs
+COPY ./rust-toolchain ./rust-toolchain
+
+# Prepare openssl arm64 libs
+RUN sed 's/^deb/deb-src/' /etc/apt/sources.list > \
+        /etc/apt/sources.list.d/deb-src.list \
+    && dpkg --add-architecture arm64 \
+    && apt-get update \
+    && apt-get install -y \
+        libssl-dev:arm64 \
+        libc6-dev:arm64
+
+ENV CC_aarch64_unknown_linux_gnu="/usr/bin/aarch64-linux-gnu-gcc"
+ENV CROSS_COMPILE="1"
+ENV OPENSSL_INCLUDE_DIR="/usr/include/aarch64-linux-gnu"
+ENV OPENSSL_LIB_DIR="/usr/lib/aarch64-linux-gnu"
+
+# Builds your dependencies and removes the
+# dummy project, except the target folder
+# This folder contains the compiled dependencies
+RUN rustup target add aarch64-unknown-linux-gnu
+RUN cargo build --release --target=aarch64-unknown-linux-gnu -v
+RUN find . -not -path "./target*" -delete
+
+# Copies the complete project
+# To avoid copying unneeded files, use .dockerignore
+COPY . .
+
+# Builds again, this time it'll just be
+# your actual source files being built
+RUN cargo build --release --target=aarch64-unknown-linux-gnu -v
+
+######################## RUNTIME IMAGE  ########################
+# Create a new stage with a minimal image
+# because we already have a binary built
+FROM resin/aarch64-debian:stretch
+
+ENV ROCKET_ENV "staging"
+ENV ROCKET_WORKERS=10
+
+RUN [ "cross-build-start" ]
+
+# Install needed libraries
+RUN apt-get update && apt-get install -y\
+    openssl\
+    ca-certificates\
+    --no-install-recommends\
+ && rm -rf /var/lib/apt/lists/*
+
+RUN mkdir /data
+
+RUN [ "cross-build-end" ]  
+
+VOLUME /data
+EXPOSE 80
+
+# Copies the files from the context (env file and web-vault)
+# and the binary from the "build" stage to the current stage
+COPY .env .
+COPY Rocket.toml .
+COPY --from=vault /web-vault ./web-vault
+COPY --from=build /app/target/aarch64-unknown-linux-gnu/release/bitwarden_rs .
+
+# Configures the startup!
+CMD ./bitwarden_rs
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