Find libffi, master branch (2022.12.08.)
Made all LCG based projects set up libffi explicitly. This is needed, because the LCG build of Python depends on a custom build of libffi.
This was discovered by @tadej on a private build of AthGeneration. Up until LCG_102b this mistake was hidden from us because the SOVERSION of libffi coming with the LCG release was the same as the version of libffi coming with CentOS 7 out of the box.
Marking this urgent, as I fear this may very well affect the AthAnalysis release that we are about to build.