lookup: skip s390 and ppc for react

[andrewhughes101]

React's failing on ppc and s390. The issue seems to be that it tries to download electron and there are no pre-compiled binaries of electron for these platforms.

Error: GET https://github.com/electron/electron/releases/download/v5.0.9/electron-v5.0.9-linux-ppc64.zip returned 404
 /home/iojs/tmp/citgm_tmp/490f84ce-553a-42cc-8633-20997dbe5f7d/react/node_modules/electron/install.js:49
   throw err
   ^
 Error: Failed to find Electron v5.0.9 for linux-ppc64 at https://github.com/electron/electron/releases/download/v5.0.9/electron-v5.0.9-linux-ppc64.zip

https://ci.nodejs.org/view/Node.js-citgm/job/citgm-smoker/

Checklist

• npm test passes
• contribution guidelines followed
  here

[codecov-io]

Codecov Report

Merging #754 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #754   +/-   ##
=======================================
  Coverage   95.44%   95.44%           
=======================================
  Files          27       27           
  Lines         879      879           
=======================================
  Hits          839      839           
  Misses         40       40

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