Fix llvm backend bins in the k derivation (#3819)

The refactor of the K derivation in #3806 broke the booster integration
test shell, because we stopped wrapping llvm-backend bins with the
`NIX_LLVM_KOMPILE_LIBS` env var. This PR restores that functionality and
I have confirmed this fixes the integration tests in booster.

nix/k.nix

@@ -55,7 +55,6 @@ let
         ln -sf ${llvm-backend}/include/kllvm-c $out/include/
         ln -sf ${llvm-backend}/lib/kllvm $out/lib/
         ln -sf ${llvm-backend}/lib/scripts $out/lib/
-        ln -sf ${llvm-backend}/bin/* $out/bin/
 
         ln -sf ${haskell-backend}/bin/kore-rpc $out/bin/kore-rpc
         ln -sf ${haskell-backend}/bin/kore-exec $out/bin/kore-exec
@@ -80,6 +79,18 @@ let
                 }"''
             }
         done
+
+        ${if (current-llvm-kompile-libs == [ ]) then ''
+          ln -sf ${llvm-backend}/bin/* $out/bin/
+        '' else ''
+          for prog in ${llvm-backend}/bin/*
+          do
+            makeWrapper $prog $out/bin/$(basename $prog) \
+              --set NIX_LLVM_KOMPILE_LIBS "${
+                lib.strings.concatStringsSep " "
+                (lib.lists.unique current-llvm-kompile-libs)
+              }"
+          done''}
       '';
 
       preFixup = lib.optionalString (!stdenv.isDarwin) ''