Interesting. On Darwin I can:
$ nix run -f <(echo 'with import <nixpkgs> {}; ffmpeg.override {libaomSupport = true;}')
and it Just Works.
On Linux if I do the same thing I get:
error: getting status of '/dev/fd/pipe:[7142756]': No such file or directory
$ nix run -f <(echo 'with import <nixpkgs> {}; ffmpeg.override {libaomSupport = true;}')
and it Just Works.
On Linux if I do the same thing I get:
error: getting status of '/dev/fd/pipe:[7142756]': No such file or directory
It wouldn't be the first time, different kernels and other system dependencies result in different workarounds.
As another example, Nix has handled some regex corner cases differently in the nix language before because the libstdc++ was different between clang (Darwin) and gcc (Linux)!
I would like it if nix run/build worked with process substitutions on Linux though. And I'm surprised, if it would break anywhere I would have expected it to break on Darwin rather than on Linux.