libnixf: parse pipe operator #3195

Job	Run time
nix-build-develop-clang (none, release, true)	3m 3s
nix-build-develop-gcc (none, release, true)	3m 6s
nix-build-develop-clang (none, release, false)	3m 10s
nix-build-develop-gcc (none, release, false)	3m 7s
nix-build-develop-clang (none, debug, true)	2m 53s
nix-build-develop-clang (none, debug, false)	2m 50s
nix-build-develop-gcc (none, debug, true)	3m 8s
nix-build-develop-gcc (none, debug, false)	3m 0s
nix-build-develop-gcc (address, release, true)	4m 44s
nix-build-develop-gcc (address, release, false)	4m 54s
nix-build-develop-gcc (address, debug, true)	4m 2s
nix-build-develop-gcc (address, debug, false)	4m 10s
nix-build-develop-gcc (undefined, release, true)	4m 13s
nix-build-develop-gcc (undefined, release, false)	4m 13s
nix-build-develop-gcc (undefined, debug, true)	3m 13s
nix-build-develop-gcc (undefined, debug, false)	3m 24s
	57m 10s

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