cli ralways eturns exitcode 0 on errors

[agreif]

1. Describe your issue:

compiling .riot file on the commandline returns always 0, even on errors.
This happens in the following cases:

for a nonexistent file:

$ ~/node_modules/.bin/riot none-xistent-file.riot
(node:25239) UnhandledPromiseRejectionWarning: Error: ENOENT: no such file or directory, stat 'none-xistent-file'
at statSync (fs.js:915:3)
...

$ echo $?
0

and also if the file exists but has no root node:

$ touch foo.riot
$ ~/node_modules/.bin/riot foo.riot 
(node:25366) UnhandledPromiseRejectionWarning: Error: [1,0]: Root tag not found.
...

$ echo $?
0

Wishful bugfix: in case of an error, a not-zeroexitcode should be returned in the shell, so that the calling process can recognize the error

2. Can you reproduce the issue?

yes, install riot cli v 4.0.3 ad do the steps in 1)

4. Which version of Riot does it affect?

   $ ~/node_modules/.bin/riot -v
   4.0.3

5. How would you tag this issue?

• Question
• [ X] Bug
• Discussion
• Feature request
• Tip
• Enhancement
• Performance

[GianlucaGuarini]

Feature added in @riotjs/[email protected]