So that things that use the makeShellWrapper/wrapProgramShell
functions can depend on makeShellWrapper explicitly, which should ease
migration in the future.
${out}/share/pixmaps and $XDG_DATA_DIRS/share/pixmaps are not part
of the freedesktop icon theme spec. /usr/share/pixmaps is. There
are some packages that have been patched to recognize this non
standard path. Those packages may be depending this path so here
we only add the equivalent hicolor theme fallback path.
Without this change the discord icon won't be picked up by apps
attempting to follow the lookup pattern in the freedesktop spec.
Chrome, Chromium, VSCode, Slack, Signal, Discord, element-desktop,
schildichat.
For the latter two, the feature flag useWayland was removed and a
wrapper script was provided.
