Closes#12071
* github.com:scylladb/scylladb:
docs/dev: building.md: mention node-exporter packages
docs/dev: building.md: replace `dev` with `<mode>` in list of debs
The developer documentation from `building.md` suggested to run unit tests with `./tools/toolchain/dbuild test` command, however this command only invokes `test` bash tool, which immediately returns with status `1`:
```
[piotrs@new-host scylladb]$ ./tools/toolchain/dbuild test
[piotrs@new-host scylladb]$ echo $?
1
```
This was probably unintended mistake and what author really meant was invoking `dbuild ninja test`.
Closes#12890
