Enviroments with CARGO_TARGET_DIR set cause builds using wasm-builder to freeze

[eopb]

This effects debug builds of substrate. I also tested with canvas-node which also uses wasm-builder and experienced the same issue.

To reproduce in docker:

FROM archlinux:latest

# Setting this env var causes build to hang indefinitely
ARG CARGO_TARGET_DIR=/target

RUN curl https://getsubstrate.io -sSf | bash -s -- --fast
RUN git clone https://github.com/paritytech/canvas-node.git
WORKDIR /canvas-node

# This command never ends
RUN source $HOME/.cargo/env && cargo build -p canvas-runtime

This docker script hangs indefinitely.

[gilescope]

Thanks - Ethan, I can confirm it hangs for me.