devel/trellis: Fix build with Python 3.8
- Backport patch from upstream repository to add Python 3.8 to the search range.
Excerpt from the log:
- Could NOT find Boost (missing: python-3.8) (found version "1.72.0")
CMake Error at CMakeLists.txt:82 (message):
No version of Boost::Python 3.x could be found.
Approved by: portmgr (build fix)