problem with 4.1.0 and cmake

Hi --

The CMakeLists.txt file in 4.1.0 doesn't seem to work properly.  I built swig using the CMakeLists.txt file, and didn't change any options other than the installation prefix.

Using the resulting swig to build a simple C++/Python test program, I get this error:  

% swig -python -c++ -o dummy.cxx dummy.i
/Users/langer/stow/swig-4.1.0/share/swig/4.1.0/swig.swg:431: Error: Syntax error in input(1).

dummy.i contains a %module line and a single function declaration.

If I instead build swig using configure and make, the error doesn't occur.

This is on a Mac running macOS 11.7, with cmake 3.23.4 provided by MacPorts.

-- Steve