The parsing done by `System.Version` does not accept a major-only string,
e.g. providing "11" would throw an exception.
Since people generally refer version as iOS 11 (and not iOS 11.0) this
is, at best, a nuisance. Xcode toolchain accept "11" as a valid string.
The first part of message was updated to show both the option name and
the (user provided) value.
The 2nd part remain the text of the .net exception message, i.e. what
`Version.Parse` tells you when it validates the string. Seeing the input
value should make it more obvious for other, incorrect version strings.
reference:
https://bugzilla.xamarin.com/show_bug.cgi?id=60280
Sebastien Pouliot