Revert "Revert "make-bootstrap-tools: try again to fix on Darwin""

This reverts commit debd401b0f.

We must not use a single-binary build for the bootstrap since the common
binary gains a dynamic linkage to gmp (due to 'factor' and 'expr'
handling arbitrary-precision arithmetic).

pkgs/stdenv/darwin/make-bootstrap-tools.nix

@@ -6,8 +6,8 @@ rec {
   coreutils_ = coreutils.override (args: {
     # We want coreutils without ACL support.
     aclSupport = false;
-    # Our tooling currently can't handle scripts in bin/, only ELFs and symlinks.
-    singleBinary = "symlinks";
+    # Problems otherwise, unlike Linux even with "symlinks".
+    singleBinary = false;
   });
 
   # Avoid debugging larger changes for now.