The Mac OS X 10.7 SDK, available in Xcode 4.1 through 4.6, is used by MEX and related capabilities. This SDK is no longer available in Xcode 5, resulting in errors similar to the following when compiling:
xcodebuild: error: SDK "macosx10.7" cannot be located.
xcrun: error: unable to find utility "clang", not a developer tool or in PATH
The simplest solution is to avoid updating Xcode to version 5 if you are using R2013a or R2013b. If you need Xcode 5, or you have already irreversibly upgraded to it, you can update MEX to use the 10.8 SDK:
1. In the MATLAB Command Window, execute the following commands:
2. Save a backup copy of this file somewhere in case you make a mistake and you need to revert your changes.
3. Scroll down to the Mac (“maci64”) section of this file, beginning around line 120.
4. Replace all instances of 10.7 with 10.8; there are four of these in all (a fifth may be found in comments only)
5. Save the file, then execute the following command in the MATLAB Command Window:
Please note that this workaround links MEX files with a different SDK than with which MATLAB was tested. Although there are no known compatibility issues, support may be limited.