Force Xcode SDK instead of CLI SDK?

[Aaron Madlon-Kay]

(Replying to list as well this time)

> > Is there a way to force use of the Xcode SDK?
>
> use_xcode yes

Sorry, I should have mentioned that I tried that, but the result was
that it still used the CLI SDK:

SDKROOT='/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk'

I am on
macOS 10.15.7 19H15
Xcode 12.2 12B45b

% ls -al /Library/Developer/CommandLineTools/SDKs
total 0
drwxr-xr-x  5 root  wheel  160 Nov 20 10:32 .
drwxr-xr-x  5 root  wheel  160 Nov 20 10:30 ..
lrwxr-xr-x  1 root  wheel   14 Nov 20 10:32 MacOSX.sdk -> MacOSX11.0.sdk
drwxr-xr-x  8 root  wheel  256 Jul 10 01:33 MacOSX10.15.sdk
drwxr-xr-x  7 root  wheel  224 Oct 20 05:39 MacOSX11.0.sdk

-Aaron