Deal with clang-cl doing the sane (but different to MSVC) thing, of
generating an empty import library, rather than silently ignoring
/IMPLIB when there are no exports.
It's a (presumably unintentional) quirk of the current implementation of
SharedLibrary.determine_filenames() that if both name_suffix and
name_prefix are set, an import library isn't generated.
Adjust test 'common/25 library versions': Make the library have exports,
so an implib is generated with MSVC. Add implib to set of files expected
to be installed
Adjust test 'common/122 shared module': Add libnosyms implib to set of
files expected to be installed, except for MSVC, where none is generated
as it has no exports
Daniel Eklöf
Jon Turney
Marco Trevisan (Treviño)
Jussi Pakkanen