Revert "Fix Implicitly Unwrapped nil value error in `XcodeSpec`"

This reverts commit ee4717ddf291b54bdc87fca7174a9e3d63228445.
Test for `.Success` and `.Failure` of `otool` in `XcodeSpec`.
Extract `buildFolderURL.URLByAppendingPathComponent`… into func.
Increase type safety with nil matcher.