Xcode 11 & SDKROOT on macOS 10.14

[Aaron Madlon-Kay]

Hi all.

I have a port that was previously working with Xcode 10.x on macOS
10.14 but is not working with Xcode 11.

I have tracked the issue down to the fact that SDKROOT is getting set
to the Command Line Tools path
(/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk) even when
setting `use_xcode yes`. (The app really does require

In portconfigure::configure_get_sdkroot (portconfigure.tcl) I see that
there is an attempt to get the SDK path from xcrun (`xcrun --sdk
macosx10.14 --show-sdk-path`) but this fails because of course(?)
Xcode 11 only has the macosx10.15 SDK. Then it falls back to the CLT.

Is this the intended behavior? It seems like there needs to be a few
more `if {![tbool use_xcode]}`s towards the end of
portconfigure::configure_get_sdkroot in order to get the right result
in this case.

Thanks,
Aaron