Fix `NSNumber.testDescription`
Fix `NSNumber.testDescription`

Apply workaround for https://bugs.swift.org/browse/SR-1464
This fixes failing `BeCloseToTest` on Linux.

jeffh/Nimble,DanielAsher/Nimble,jeffh/Nimble,abbeycode/Nimble,DanielAsher/Nimble,abbeycode/Nimble,abbeycode/Nimble,AnthonyMDev/Nimble,phatblat/Nimble,AnthonyMDev/Nimble,Quick/Nimble,twobitlabs/Nimble,Quick/Nimble,abbeycode/Nimble,twobitlabs/Nimble,dgdosen/Nimble,twobitlabs/Nimble,DanielAsher/Nimble,dgdosen/Nimble,AnthonyMDev/Nimble,jeffh/Nimble,phatblat/Nimble,Quick/Nimble,phatblat/Nimble,dgdosen/Nimble,dgdosen/Nimble,jeffh/Nimble