add upload rsync binary step for the ssh devices

[MarcTreySonos]

on some ssh devices rsync is not necessarily installed.

this allow the upload of a pre-build rsync binary on the target ssh device, useful if /usr/bin/rsync does not exists on the target, this is done by adding install_adhoc_rsync_local_path in the dinghy.toml:

[platforms.rsync-test]
rustc_triple='aarch64-unknown-linux-gnu'
toolchain='/home/treym//toolchains/rsync-test/aarch64-unknown-linux-gnu'

[ssh_devices]
ci-rsync-test-001 = { hostname = "192.168.1.34", username="test", platform="rsync-test", install_adhoc_rsync_local_path="/home/treym/toolchains/rsync-test/prebuilt/bin/rsync" }

[kali]

Can we move it the configuration file instead ? I'd like to maintain the "setup each device once, run in any project with no hassle" spirit ?

[MarcTreySonos]

[platforms.rsync-test]
env={ DINGHY_RSYNC_PATH='/tmp/rsync' }
rustc_triple='aarch64-unknown-linux-gnu'
toolchain='/home/treym//toolchains/rsync-test/aarch64-unknown-linux-gnu'

[ssh_devices]
ci-rsync-test-001 = { hostname = "192.168.1.34", username="test", platform="rsync-test" }

in can be stored in the dinghy.toml file on a per platform basis , would that be hassle free spirit enough ? @kali