databases/mongodb50: Fix build failure with scons 4.2.0 by using in source scons 3.1.2
- Fix scons by using in source scons 3.1.2 (They are planning to move to Scons 4.2.0 in the future)
- Disable LTO on clang12/aarch64, bug #257765
- Build already installs in $STAGEDIR, so only strip in do-install.
- Fix a portlint warnings about the comment at the LICENSE section.
PR: 257925