dmraid: fix w/musl (missing includes, -D_GNU_SOURCE)

[dtzWill]

Requires patching systemd to work w/musl to test on master, but still good to fix.

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: dmraid

Partial log (click to expand)

/nix/store/ngz7ff4drhzx5hndpqpj1md2pzzckgzc-dmraid-1.0.0.rc16

[GrahamcOfBorg]

No attempt on x86_64-darwin (full log)

The following builds were skipped because they don't evaluate on x86_64-darwin: dmraid

Partial log (click to expand)

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

[dtzWill]

No rebuilds for non-musl (by design), merging.

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Attempted: dmraid

Partial log (click to expand)

these paths will be fetched (1.43 MiB download, 7.18 MiB unpacked):
  /nix/store/jr6rf21pssjfh5mjmdngkv6zhacqjc5w-dmraid-1.0.0.rc16
  /nix/store/r7d0z538y3wip4hfbx0inhqh76ly86wh-lvm2-2.02.177
copying path '/nix/store/r7d0z538y3wip4hfbx0inhqh76ly86wh-lvm2-2.02.177' from 'https://cache.nixos.org'...
copying path '/nix/store/jr6rf21pssjfh5mjmdngkv6zhacqjc5w-dmraid-1.0.0.rc16' from 'https://cache.nixos.org'...
/nix/store/jr6rf21pssjfh5mjmdngkv6zhacqjc5w-dmraid-1.0.0.rc16