Provide an end-of-build message

[javaducky]

Addresses issue #38.

Example output:

I didn't add the output to the log, preferring plain stdout. WDYT? Timestamps and level just seemed superfluous.

[javaducky]

./xk6 build \
  --with github.com/grafana/xk6-output-prometheus-remote \
  --with github.com/grafana/xk6-output-timescaledb \
  --output /tmp/my-k6

produces the following:

[mstoykov]

LGTM! just wondering if the extra information added isn't going to be more confusing then not.

[mstoykov]

I wonder if this is necessary given that it was just provided as arguments. Especially as if replace and specific versions were used it might also be a bit confusing - not giving that information here as well.

[javaducky]

True. I was originally thinking to include version as well, but seemed like a potential rabbit-hole for little benefit. 😄

[javaducky]

So @mstoykov @imiric, what if we only display a basic message if the --output is not provided to simply avoid confusion for the default k6 binary? That way, an "advanced user" can override settings and will know where the new binary is going to be, whereas a new user that is simply relying on defaults will have the warning that this is not the k6 that is on their system path.

For example:

NOTE: xk6 has now produced a new k6 binary in <current directoy>.

This _may_ be different than the k6 command on your system path.

This will simplify the "edge" cases, but hopefully not be more confusing 😆. For this, I'd add to logger at WARN level. WDYT?

[javaducky]

How about this? (only if --output option is specified)

[imiric]

Sure, I think this will still be helpful.

Although, it's the wrong suggestion on Windows. I think it will fail there...

EDIT: Nevermind, it works fine 🎉:

2nd although 😄: this warning is actually irrelevant on Windows, since all shells run binaries in the CWD first by default and then check the PATH, so plain k6 (no .\k6) will run the just built binary. Yeah, huge security risk, but that's Windows... 😅