Eliminate duplication in building the list of external libraries
to link to between SConstruct and src/SConscript.

On macOS, sysconfig.get_platform() returns a string like
'macosx-11.0-arm64', but the wheel filename will actually contain
'macosx_11_0_arm64'.

This prevents rebuilds of the wheel file every time 'scons build'
is run because the actual wheel file doesn't match the expected name.

Co-authored-by: Bryan W. Weber <bryan.w.weber@gmail.com>

Something changed in setuptools that causes the old method of forcing
platform-specific wheels to be built to break for certain configurations
(specifically, Windows builds with Python 3.7). This alternative approach
appears to be more robust.

Also increase the logging from 'pip wheel' to help with debugging

The old way of handling declarations for static members of a
template class was weird and required different implementations for
different compilers. This approach is standards-conformant and works
everywhere.