Undefined stg_sel_17_upd_info symbols on OS X

Several people have reported that recent ghc-8.0 and master snapshots fail to build on OS X,

  HC [stage 1] ghc/stage2/build/tmp/ghc-stage2
Warning: -rtsopts and -with-rtsopts have no effect with -no-hs-main.
    Call hs_init_ghc() from your main() function to set these options.
Undefined symbols for architecture x86_64:
  "_stg_sel_17_upd_info", referenced from:
      _s1s8Z_info in UI.dyn_o
      _s1s9w_info in UI.dyn_o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
`gcc' failed in phase `Linker'. (Exit code: 1)

These were originally introduced in #11155 (closed), although this appears to be a much different beast from the original issue that ticket was reporting: the symbols in question here are updatable selector closures, not application closures like in #11155 (closed).