test: handle undefined default_configuration

[codebytere]

This PR adds a check for process.config.target_defaults being undefined, as it is Electron's case, and ensures that the buildType is set to a default value of Release should it not be defined.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/26548/

[codebytere]

@trivikr your suggestion failed lint:

/home/travis/build/nodejs/node/test/common/index.js
  122:4  error  '?' should be placed at the end of the line  operator-linebreak
  123:4  error  ':' should be placed at the end of the line  operator-linebreak

are we fine for me to move back to the previous format?

I could also do this:

const buildType = process.config.target_defaults ?
  process.config.target_defaults.default_configuration :
  'Release';

i'm fairly un-opinionated on this front ¯\_(ツ)_/¯

[trivikr]

Sure, this format works

const buildType = process.config.target_defaults ?
  process.config.target_defaults.default_configuration :
  'Release';

I'd posted my review as a nit, suggesting it's optional.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/26635/

[codebytere]

Landed in 70281ce