pkg: handle undefined vars in command filters (#11512) #293

Job	Run time
Build microbenchmarks	2m 33s
Build (macos-latest, 5.1.x)	21m 36s
Create local opam switch (macos-latest, 5)	9m 16s
Build (ubuntu-latest, 5.1.x)	11m 22s
Coq 8.16.1	7m 12s
Create local opam switch (macos-latest, 4.14)	8m 42s
Build (ocaml-variants.5.4.0+trunk, ubuntu-latest, true)	5m 43s
Documentation	3m 22s
Create local opam switch (ubuntu-latest, 5)	8m 30s
Build (4.14.x, ubuntu-latest, true)	5m 17s
Create local opam switch (ubuntu-latest, 4.14)	7m 46s
Build (4.14.x, macos-latest, true)	3m 7s
Format	1m 6s
Build (5.1.x, macos-13, true)	7m 48s
Build monorepo benchmark docker image	1m 46s
Build (ocaml-base-compiler.4.14.2,system-msvc, windows-latest)	15m 12s
Nix (macos-latest)	2m 9s
Wasm_of_ocaml	6m 35s
Build (ocaml-base-compiler.5.1.1,system-mingw, windows-latest)	8m 2s
Nix (ubuntu-latest)	52s
Build (4.08.x, ubuntu-latest, true)	5m 36s
	2h 23m 32s

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