nixd/Controller: report error on `textDocument/definition` on builtins #3155

Job	Run time
nix-build-develop-clang (none, release, true)	3m 1s
nix-build-develop-gcc (none, release, true)	3m 10s
nix-build-develop-clang (none, release, false)	2m 59s
nix-build-develop-gcc (none, release, false)	3m 3s
nix-build-develop-clang (none, debug, true)	2m 52s
nix-build-develop-gcc (none, debug, true)	3m 6s
nix-build-develop-clang (none, debug, false)	2m 42s
nix-build-develop-gcc (none, debug, false)	2m 57s
nix-build-develop-gcc (address, release, true)	4m 40s
nix-build-develop-gcc (address, release, false)	4m 38s
nix-build-develop-gcc (address, debug, true)	3m 55s
nix-build-develop-gcc (address, debug, false)	3m 56s
nix-build-develop-gcc (undefined, release, true)	4m 7s
nix-build-develop-gcc (undefined, release, false)	4m 5s
nix-build-develop-gcc (undefined, debug, true)	3m 20s
nix-build-develop-gcc (undefined, debug, false)	3m 29s
	56m 0s

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