absolutePathOrEmpty + other fixes
absolutePathOrEmpty + other fixes

- absolutePathOrEmpty
- fix xcodeProjectDir break
- comment fixes
- tabs => spaces

nirmaljuthani/j2objc-gradle,madvay/j2objc-gradle,j2objc-contrib/j2objc-gradle,brunobowden/j2objc-gradle,madvay/j2objc-gradle,brunobowden/j2objc-gradle,j2objc-contrib/j2objc-gradle,madvay/j2objc-gradle,j2objc-contrib/j2objc-gradle,madvay/j2objc-gradle,j2objc-contrib/j2objc-gradle,nirmaljuthani/j2objc-gradle,confile/j2objc-gradle,confile/j2objc-gradle,maxbritto/j2objc-gradle,maxbritto/j2objc-gradle,brunobowden/j2objc-gradle,brunobowden/j2objc-gradle,maxbritto/j2objc-gradle,maxbritto/j2objc-gradle