--ignore flag being ignored in Jenkins environment about uglifyify

[Kalvin126]

@danfinlay unfortunately #62 does not fix my issue 😕 I now encounter a crash:

[20:57:38]: ▸ DefaultsError: `ignore` is not a supported option while parsing file: ***/node_modules/***-sdk/build/index.js
[20:57:38]: ▸ at DefaultsError.Object.defineProperty.get (eval at <anonymous> (***/node_modules/uglify-es/tools/node.js:21:1), <anonymous>:75:23)
[20:57:38]: ▸ at Readable.errorExit (***/node_modules/browserify/bin/cmd.js:68:26)
[20:57:38]: ▸ at emitOne (events.js:77:13)
[20:57:38]: ▸ at Readable.emit (events.js:169:7)
[20:57:38]: ▸ at Labeled.<anonymous> (***/node_modules/read-only-stream/index.js:27:44)
[20:57:38]: ▸ at emitOne (events.js:77:13)
[20:57:38]: ▸ at Labeled.emit (events.js:169:7)
[20:57:38]: ▸ at Labeled.<anonymous> (***/node_modules/stream-splicer/index.js:133:18)
[20:57:38]: ▸ at emitOne (events.js:82:20)
[20:57:38]: ▸ at Labeled.emit (events.js:169:7)

[Kalvin126]

ah yes, as described in #73, ignore flag looks to be broken in 4.0.0 +