[clang] [clang] Fixup last value in DarwinPlatformKind enum (PR #81011)

[Juergen Ributzka via cfe-commits]

ributzka wrote:

> Why didn't this trigger:
> 
> https://github.com/llvm/llvm-project/blob/ab92f6274b7c3a4b4445d47017bc481aa919545f/clang/lib/Driver/ToolChains/Darwin.cpp#L1906
> 
> ?

XROS is missing in the env vars too: https://github.com/llvm/llvm-project/blob/ab92f6274b7c3a4b4445d47017bc481aa919545f/clang/lib/Driver/ToolChains/Darwin.cpp#L1899

https://github.com/llvm/llvm-project/pull/81011