[Nix-dev] [***SPAM***] re2c fix build

[Karn Kallio via nix-dev]

The attached patch fixes the build of the re2c Nixpkgs expression by
adjusting the sourceRoot to account for the unpackFile treatment of a
directory.

[Vincent Laporte via nix-dev]

Applied as ee5a17514c500244b2911c80f3d42311bdf97491. Thanks.

[Vladimír Čunát via nix-dev]

Post by Karn Kallio via nix-dev
The attached patch fixes the build of the re2c Nixpkgs expression by
adjusting the sourceRoot to account for the unpackFile treatment of a
directory.

Note: I had to "undo" that anyway in 3a891c67fc87, as the change was
caused by commits that I didn't manage to fixup before they reached master.

--Vladimir