meson: create a symlink for pipewire-pulse instead of building binary twice

Because meson does not have native support for symlinks.
See https://github.com/mesonbuild/meson/issues/1602

Inspired by xserver:
xorg/xserver@a3931ec6
41 jobs for wip/daissi/meson_symlink in 8 minutes and 43 seconds (queued for 2 seconds)
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