Adds run-xcodebuild function to wrap xcodebuild calls to keep logging
and error handling consistent. Currently used only by the iOS build; the
macOS build has a corresponding execBuildCommand function which does
pretty much the same thing (changing that would belong in a separate PR
I think and low priority.)
When working on a new build script, I tripped over the `-?` question
mark help parameter here, as it needs to be escaped. Opted to fix all
the instances in our scripts, although AFAICT there would not have been
current bugs arising from this, as there were no conflicting one
character options lower in the case list.
