flake: use stdenvNoCC

[GrigorenkoPV]

Drastically reduces the size of build dependencies by not pulling gcc.

Before:

$ nix -Lv build . --dry-run
this derivation will be built:
  /nix/store/516w6ydn8v54bb5na9lcgwjn4dqpi7yn-xdg-ninja-0.1.0.drv
these 54 paths will be fetched (74.11 MiB download, 341.59 MiB unpacked):
...

After:

$ nix -Lv build . --dry-run
this derivation will be built:
  /nix/store/11mifcs2x0ngca6l9gklwz8zwjp87k15-xdg-ninja-0.1.0.drv
these 41 paths will be fetched (18.35 MiB download, 87.14 MiB unpacked):
...