Sound is broken when wxwidgets3.2 is compiled without SDL

[Eugene San]

By default WXWidgets compiles without SDL support and as result it only supports OSS as a sound backend.
On modern systems native OSS support is not available and previously available workaround like "osspd" no longer compatible with modern systems running pipeWire or inside containers.

As a solution I suggest adding "libsdl2-dev" to build-deps and "--with-sdl" to configure options.

The change is trivial and results in a build that solves the issue and doesn't require rebuilding other packages.

Patched "wxwidgets3.2 - 3.2.6+dfsg-2ubuntu1" works on both Noble and Plucky.
Tested with wx3.2-examples and freefilesync.