Emscripten: Different platforms produce different output filenames

[crazydef]

When building for Emscripten the generated library names are different depending on the host platform.

This is obviously in part due to me using --library-suffix=.web.Debug.

On Linux I get: libbotan.web.Debug-3.a
While MacOS gives me: libbotan-3.web.Debug.a

Not impossible to workaround, but a bit weird nonetheless. :)