fix builds on macOS when kernel modules are used

The mac implementation of sed has different requirements for the -i
option. Instead of using that, just redirect the output to the final
location of modules.dep, since it's being copied in the very next
line anyway.

Bug: 38268091
Test: run build with kernel modules on macOS
Change-Id: I49e4a1a69f01139ef47711ab1223d3a8e5cda568