qgrep: fix darwin and aarch64-linux build

https://hydra.nixos.org/build/108321871
https://hydra.nixos.org/build/108556036

Things done:

* SSE2 isn't available for the aarch64-target of GCC (the package builds
  on aarch64 without those flags and works fine as well).

* Added missing darwin libraries.

* Applied a darwin-specific patch which disables i386 as target platform
  (breaks at least on MacOS catalina otherwise).