Allow comma in buildSettings

when i try to set "TARGETED_DEVICE_FAMILY", it failed.
buildSettingsObj.TARGETED_DEVICE_FAMILY = '1,2'

```
While preparing Cordova project for platform iOS:
SyntaxError: Expected ".", "/*", ";", or [0-9] but "," found.
at peg$buildStructuredError (/Users/monsterstep/.meteor/packages/meteor-tool/.1.9.0.1eehdch.kfff++os.osx.x86_64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.x86_64/dev_bundle/lib/node_modules/cordova-lib/node_modules/xcode/lib/parser/pbxproj.js:412:12)
at Object.peg$parse [as parse] (/Users/monsterstep/.meteor/packages/meteor-tool/.1.9.0.1eehdch.kfff++os.osx.x86_64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.x86_64/dev_bundle/lib/node_modules/cordova-lib/node_modules/xcode/lib/parser/pbxproj.js:1886:11)
```

the xcodeproj has value like this



https://github.com/apache/cordova-node-xcode/issues/57

Start with the pbxproj.js parser referenced in the error and trace how buildSettingsObj.TARGETED_DEVICE_FAMILY is parsed or serialized. Reproduce the failure with the value '1,2', then verify that the Xcode project value is accepted without the reported comma syntax error.

Written by the indexing model from the issue text.