Fix cram tests build-path-prefix-map substitutions #29720

Job	Run time
Nix (macos-latest)	2m 32s
Build (macos-latest, 5.1.x)	11m 44s
Nix (ubuntu-latest)	57s
Documentation	59s
Build (ubuntu-latest, 5.1.x)	9m 35s
Coq 8.16.1	7m 14s
Format	1m 10s
Wasm_of_ocaml	11m 0s
Build (ocaml-variants.5.4.0+trunk, ubuntu-latest, true)	1m 30s
Build microbenchmarks	2m 38s
Build (4.14.x, ubuntu-latest, true)	1m 29s
Build (4.14.x, macos-latest, true)	2m 22s
Create local opam switch (macos-latest, 5)	6m 37s
Build (5.1.x, macos-13, true)	4m 19s
Build monorepo benchmark docker image	3m 36s
Create local opam switch (macos-latest, 4.14)	6m 41s
Create local opam switch (ubuntu-latest, 5)	5m 15s
Build (ocaml-base-compiler.4.14.2,system-msvc, windows-latest)	14m 11s
Build (ocaml-base-compiler.5.1.1,system-mingw, windows-latest)	8m 29s
Create local opam switch (ubuntu-latest, 4.14)	5m 1s
Build (4.08.x, ubuntu-latest, true)	1m 26s
Build (4.04.x, ubuntu-latest, true, true)	4m 30s
Build (4.02.x, ubuntu-latest, true)	3m 58s
	1h 57m 13s

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