Use single target build directory

[dapplion]

When the dappnodesdk builds it uses the uncommon approach of creating a separate build directory for each version. This results in packages directories full of

build_0.2.0
build_0.2.1
build_0.2.2
build_0.2.3
build_0.2.4

This PR changes the behaviour to use the same target build regardless of version customizable with

--build_dir ./some_other_dir

If a user wants the same behaviour as before and keep backups of each version, just do

dappnodesdk build && cp -r build build_0.2.0

Extracted from #213

[github-actions]

DAppNode bot has built and pinned the release to an IPFS node, for commit: 04603b9

This is a development version and should only be installed for testing purposes, install link

/ipfs/QmT68n96ZDwRiy8SN5qr6AkrzD8mVaambCixHpdmu9PqDa

(by dappnodebot/build-action)

[pablomendezroyo]

Requires more work