docker: fix build on arm64 architecture

[tiborsimko]

Closes reanahub/reana#753.

[mdonadoni]

(Disclaimer: I have not tested this)

For reana-ui we are using a multi-stage build, where the first stage builds all the static files (js, css, etc.) while the second stage is just a simple nginx server that serves these static assets. These assets do not depend on the architecture, as they are just JS/CSS sources/images.

In this case we should be able to run the first stage always in the native architecture of the builder and after that run the second stage in the target architecture (possibly emulated), as explained here: https://www.docker.com/blog/faster-multi-platform-builds-dockerfile-cross-compilation-guide/

This does not bring advantages when the build architecture and the target architecture are the same, but it should make cross-building faster

As far as I can tell, it's only necessary to change this first line:

Suggested change

	FROM docker.io/library/node:18 as react-build
	FROM --platform=$BUILDPLATFORM docker.io/library/node:18 as react-build

[tiborsimko]

OK, I can test it this evening.

[mdonadoni]

Locally I see some network timeouts, probably due to emulation slowness. This fixes it:

Suggested change

	yarn && \
	yarn --network-timeout 600000 && \