fix: attempt to make linux builds faster (#911)

This work aims to make Linux builds faster to make https://github.com/ooni/probe/issues/2249 more convenient. Since those builds runs inside Docker, the problem to solve here is to save/restore the Go caches notwithstanding Docker. Because Docker runs as root, we need to modify the build a bit to run as a normal user. Otherwise, we will not be able to save the Go cache using actions/cache@v3. (Other approaches such as using `sudo` are possible but running the build as an unprivileged user actually looks cleaner, so I chose to do that.) While there, add a `.editorconfig`.

CLI/go-build-alpine

@@ -1,15 +1,11 @@
 #!/bin/sh
 set -euxo pipefail
-apk update
-apk upgrade
-apk add --no-progress gcc git linux-headers musl-dev
-# We need to force git to look into this repository owned by the
-# user outside docker rather than by the user running docker
-git config --global --add safe.directory $(pwd)
 # Some of the following exports are redundant but are however
 # useful because they provide explicit logging
 export CGO_ENABLED=1
 export GOARM=$GOARM
+export GOCACHE=$GOCACHE
+export GOMODCACHE=$GOMODCACHE
 export GOOS=$GOOS
 export GOARCH=$GOARCH
 for PACKAGE in $@; do