I have a similar problem of not finding MacOSX13.1.sdk when building a kernel on MacOS12.6.4. I see these files in .../Platforms/MacOSX.platform/Developer/SDKs: drwxr-xr-x 7 root wheel 224 Nov 12 13:18 MacOSX.sdk lrwxr-xr-x 1 root wheel 10 Mar 10 09:26 MacOSX13.1.sdk -> MacOSX.sdk lrwxr-xr-x 1 root wheel 10 Mar 10 09:26 MacOSX13.sdk -> MacOSX.sdk So one reason for failure might be over-zealous search for a directory only, and not allowing symbolic links.