migrate Dockerfile away from rust-musl-builder

Dockerfile

@@ -1,32 +1,26 @@
-FROM ekidd/rust-musl-builder:beta as build
+FROM rust:alpine3.14 as builder
 
-USER rust
-WORKDIR /home/rust/src/
-RUN USER=rust cargo new datatrash
+WORKDIR /app
+RUN apk add musl-dev
 
-WORKDIR /home/rust/src/datatrash
-COPY --chown=rust Cargo.toml Cargo.lock ./
-RUN cargo build --release
+RUN cargo init
+COPY Cargo.toml Cargo.lock ./
+RUN cargo build --release --target=x86_64-unknown-linux-musl
 
-COPY --chown=rust src ./src
-COPY --chown=rust static ./static
-COPY --chown=rust template ./template
-COPY --chown=rust snippet ./snippet
-COPY --chown=rust init-db.sql ./init-db.sql
+COPY src ./src
+COPY static ./static
+COPY template ./template
+COPY snippet ./snippet
+COPY init-db.sql ./init-db.sql
 RUN touch src/main.rs
-RUN cargo build --release
-RUN strip target/x86_64-unknown-linux-musl/release/datatrash
+RUN cargo build --release --target=x86_64-unknown-linux-musl
+RUN strip /app/target/x86_64-unknown-linux-musl/release/datatrash
 
-FROM alpine:latest
 
-ENV RUST_BACKTRACE "1"
 
-RUN mkdir /opt/datatrash
-WORKDIR /opt/datatrash
+FROM alpine:3.14
 
-COPY --from=build \
-    /home/rust/src/datatrash/target/x86_64-unknown-linux-musl/release/datatrash \
-    /opt/datatrash/
+COPY --from=builder /app/target/x86_64-unknown-linux-musl/release/datatrash /opt/datatrash/
 COPY static /opt/datatrash/static
 RUN mkdir /opt/datatrash/files