Unreg build failed as:

  $ ./configure --enable-unregisterised
  $ make

  HC [stage 1] libraries/ghc-prim/dist-install/build/GHC/PrimopWrappers.o
    ghc_1.hc: In function 'ghczmprim_GHCziPrimopWrappers_pdep8zh_entry':

    ghc_1.hc:1810:9: error:
     error: implicit declaration of function 'hs_pdep8'; did you mean 'hs_ctz8'?
       [-Werror=implicit-function-declaration]
     _c3jz = hs_pdep8(*Sp, Sp[1]);
             ^~~~~~~~
             hs_ctz8
       |
  1810 | _c3jz = hs_pdep8(*Sp, Sp[1]);
       |         ^

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>