`cargo codspeed build` not support multiple `--package` flags

[EYHN]

example

cargo codspeed build -p crate1 -p crate2 

which is supported by cargo build

[art049]

As discussed on Discord, for now a possible workaround is to run the build command multiple times:

cargo codspeed build -p crate1
cargo codspeed build -p crate2

We'll implement the behavior soon, though!