libnixf: parse pipe operator #3191

Job	Run time
nix-build-develop-clang (none, release, true)	2m 58s
nix-build-develop-gcc (none, release, true)	3m 3s
nix-build-develop-clang (none, release, false)	3m 1s
nix-build-develop-gcc (none, release, false)	3m 8s
nix-build-develop-clang (none, debug, true)	2m 50s
nix-build-develop-gcc (none, debug, true)	2m 59s
nix-build-develop-clang (none, debug, false)	2m 48s
nix-build-develop-gcc (none, debug, false)	3m 6s
nix-build-develop-gcc (address, release, true)	4m 50s
nix-build-develop-gcc (address, release, false)	4m 55s
nix-build-develop-gcc (address, debug, true)	3m 54s
nix-build-develop-gcc (address, debug, false)	3m 57s
nix-build-develop-gcc (undefined, release, true)	4m 18s
nix-build-develop-gcc (undefined, release, false)	4m 18s
nix-build-develop-gcc (undefined, debug, true)	3m 19s
nix-build-develop-gcc (undefined, debug, false)	3m 23s
	56m 47s

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