Tundra nil Depends repo

a.c

int a()
{
  return 3;
}

b.c

int b()
{
  return 5;
}

c.c

#include <stdio.h>

int a();
int b();

int main()
{
  printf("%i\n", a(), b());
  return 0;
}

tundra.lua

Build {
    Configs = {
        {
            Name = "win64-msvc",
            DefaultOnHost = "windows",
            Tools = {
                {
                    "msvc-vs2019",
                    TargetArch = "x64"
                }
            }
        }
    },
    Units = {
        function()
            StaticLibrary {
                Name = "a",
                Sources = {
                    "a.c"
                }
            }

            StaticLibrary {
                Name = "b",
                Sources = {
                    "b.c"
                }
            }

            Program {
                Name = "c",
                Depends = {
                    nil, -- remove this to successfully compile
                    "a",
                    "b"
                },
                Sources = {
                    "c.c"
                }
            }

            Default "c"
        end

    }
}