Swig is preparing release of new version 4.1.0. I was testing the rebuild of the package with the version and it failed. The reason is this change https://github.com/swig/swig/issues/2193 #2193 -DFOO on the SWIG command line now sets FOO to 1 for consistency with C/C++ compiler preprocessors. Previously SWIG set FOO to an empty value. Existing invocations of SWIG with `-DFOO` where the empty value matters can be updated to `-DFOO=` which should work with both old and new releases of SWIG. *** POTENTIAL INCOMPATIBILITY *** The issue was reported to upstream and it was fixed.
Could you please backport the upstream fix? New swig should be release soon.