stdenv: Replace "// optionalAttrs" with nullable attr name

As in https://github.com/NixOS/nixpkgs/pull/430132, it saves a lot of
set allocations and merge operations, but makes code harder to read.

I've tried introducing a function like this to make code cleaner, but it
increases number of envs and space taken by them significantly:

  optionalAttr = cond: name: if cond then name else null;

I've also tried applying this logic to the section with isDarwin, but
it makes things measurably worse for x86_64-linux eval.

0 files changed, 0 insertions, 0 deletions