Getting "Layer already exists" for project built with docker

FROM rust:latest as builder

RUN cargo new --bin app

WORKDIR /app

COPY ./Cargo.toml ./Cargo.toml
COPY ./Cargo.lock ./Cargo.lock

RUN cargo build --release
RUN rm src/*.rs

COPY ./src ./src
COPY ./migrations ./migrations
COPY ./diesel.toml ./diesel.toml

RUN cargo build --release

FROM rust:latest

RUN apt-get update && apt-get install --yes libsqlite3-dev

ENV PORT=3000
EXPOSE ${PORT}

WORKDIR /app

COPY --from=builder /app/target/release/make_an_api_in_rust /app/make_an_api_in_rust

CMD ["/app/make_an_api_in_rust"]

FROM rust:latest as builder

RUN cargo new --bin app

WORKDIR /app

COPY ./Cargo.toml ./Cargo.toml
COPY ./Cargo.lock ./Cargo.lock

RUN cargo build --release
RUN rm src/*.rs

COPY ./src ./src
COPY ./migrations ./migrations
COPY ./diesel.toml ./diesel.toml

RUN cargo build --release

FROM rust:latest

RUN apt-get update && apt-get install --yes libsqlite3-dev

ENV PORT=3000
EXPOSE ${PORT}

WORKDIR /app

COPY --from=builder /app/target/release/make_an_api_in_rust /app/make_an_api_in_rust

CMD ["/app/make_an_api_in_rust"]