Fix apparent nondeterminism in pattern matching compilation. (#7557) #7128

Job	Run time
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	2m 28s
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	4m 18s
build-compiler (macos-13, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	5m 40s
build-compiler (ubuntu-24.04, ocaml-variants.5.0.0+options,ocaml-option-static, linux-x64, x86_64...	2m 19s
build-compiler (macos-14, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	2m 59s
build-compiler (windows-latest, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu)	13m 15s
build-compiler (ubuntu-24.04, ocaml-variants.5.2.1+options,ocaml-option-static, linux-x64, x86_64...	2m 2s
build-compiler (ubuntu-24.04, ocaml-variants.4.14.2+options,ocaml-option-static, linux-x64, x86_6...	2m 20s
pkg-pr-new	49s
api-docs	2m 35s
test-integration (macos-13)	1m 11s
test-integration (macos-14)	42s
test-integration (windows-latest)	2m 1s
test-integration (ubuntu-24.04-arm)	41s
test-integration (ubuntu-24.04)	35s
publish	0s
	43m 55s

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