Fix for multy: line 1: /multy/multy-back: not found

[abitrolly]

This image is built and deployed successfully, but fail to run:

Multy-back/Dockerfile

Lines 24 to 27 in 822857b

	FROM base as multy-back
	WORKDIR /multy
	COPY --from=builder /go/src/github.com/Multy-io/Multy-back/cmd/multy-back/multy-back /multy/multy-back
	ENTRYPOINT /multy/multy-back

$ docker run multyio/multy-back
/bin/sh: /multy/multy-back: not found

Because:

https://stackoverflow.com/questions/34729748/installed-go-binary-not-found-in-path-on-alpine-linux-docker

CC @Enmk

[abitrolly]

Need to compile with musl, which is the default replacement for glibc on Apline.

[Enmk]

Fixed in 'dev' branch with PR #125