# cat darling.nix
with import <nixpkgs> {};

fetchzip {
   url = "https://github.com/darlinghq/darling/archive/d2cc5fa748003aaa70ad4180fff0a9a85dc65e9b.tar.gz";
   sha256 = "0krlrb75fcfa52kx1nvlpyxk060zk2931hfw6g86k5nmzfv9hyxa";
   postFetch = ''
     # Get rid of case conflict
     mkdir $out
    cd $out
    tar -xzf $downloadedFile --strip-components=1
    rm -r $out/src/libm
  '';
}
# nix-build darling.nix -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/4f3475b113c93d204992838aecafa89b1b3ccfde.tar.gz
these derivations will be built:
  /nix/store/3gsv7n0n25h7f9k6vmnq42ssjlbyk823-source.drv
building '/nix/store/3gsv7n0n25h7f9k6vmnq42ssjlbyk823-source.drv'...

trying https://github.com/darlinghq/darling/archive/d2cc5fa748003aaa70ad4180fff0a9a85dc65e9b.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   159  100   159    0     0    703      0 --:--:-- --:--:-- --:--:--   706
100 12.5M    0 12.5M    0     0  5154k      0 --:--:--  0:00:02 --:--:-- 5967k
hash mismatch in fixed-output derivation '/nix/store/a18g6gvfs8xbw33a9hq9nh3g3sl8r83p-source':
  wanted: sha256:0krlrb75fcfa52kx1nvlpyxk060zk2931hfw6g86k5nmzfv9hyxa
  got:    sha256:11b51fw47nl505h63bgx5kqiyhf3glhp1q6jkpb6nqfislnzzkrf
error: build of '/nix/store/3gsv7n0n25h7f9k6vmnq42ssjlbyk823-source.drv' failed

% find result/ | tr '[:upper:]' '[:lower:]' | sort | uniq -d
result/src/opendirectory

# cat darling.nix 
with import <nixpkgs> {};

fetchzip {
   url = "https://github.com/darlinghq/darling/archive/d2cc5fa748003aaa70ad4180fff0a9a85dc65e9b.tar.gz";
   sha256 = "0krlrb75fcfa52kx1nvlpyxk060zk2931hfw6g86k5nmzfv9hyxa";
   postFetch = ''
     # Get rid of case conflict
     mkdir $out
    cd $out
    tar -xzf $downloadedFile --strip-components=1
    rm -r $out/src/libm

    # A workaround for case-sensitive filesystems
    mv src/opendirectory/* src/OpenDirectory/
    rmdir src/opendirectory
  '';
}
# nix-build darling.nix                                                                     
these derivations will be built:
  /direct/star+u/veprbl/nix/store/bz7gaqvm0s9zmn66frkilhrlpa5b7qqj-source.drv
building '/direct/star+u/veprbl/nix/store/bz7gaqvm0s9zmn66frkilhrlpa5b7qqj-source.drv'...

trying https://github.com/darlinghq/darling/archive/d2cc5fa748003aaa70ad4180fff0a9a85dc65e9b.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   159  100   159    0     0   1186      0 --:--:-- --:--:-- --:--:--  1177
100 12.5M    0 12.5M    0     0  5197k      0 --:--:--  0:00:02 --:--:-- 6128k
hash mismatch in fixed-output derivation '/direct/star+u/veprbl/nix/store/b2q69zj566wqhy0rg0ff6j6clqrzwb46-source':
  wanted: sha256:0krlrb75fcfa52kx1nvlpyxk060zk2931hfw6g86k5nmzfv9hyxa
  got:    sha256:11b51fw47nl505h63bgx5kqiyhf3glhp1q6jkpb6nqfislnzzkrf
error: build of '/direct/star+u/veprbl/nix/store/bz7gaqvm0s9zmn66frkilhrlpa5b7qqj-source.drv' failed