Merge branch 'meson-optional-rt' of https://github.com/jwillikers/util-linux

* 'meson-optional-rt' of https://github.com/jwillikers/util-linux:
  meson: Only pick up the rt library once
  meson: Add build-lsfd option and make rt dependency optional

diff --cc meson.build
Simple merge

diff --cc meson_options.txt
Simple merge