BUILD: Build libdlopen_test_providers.la as a dynamic library
    
    Module which can be loaded by dlopen but cannot be linked with
    other binaries.
    
    *** Warning: Linking the executable test_xyzp against the loadable module
    *** libdlopen_test_providers.so is not portable!
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    (cherry picked from commit 1116fbbf0e50827841a6bafd80c027c3d3548c1f)