build

Reinstate #4772, with reducibility check #23239

Job	Run time
runtime5 poll-insertion (x86_64-linux)	7m 49s
runtime4 O3 (x86_64-linux)	7m 30s
runtime5 multidomain (x86_64-linux)	8m 47s
runtime5 debug (x86_64-linux)	9m 59s
runtime5 dev (x86_64-linux)	7m 0s
runtime5 debug stack-checks (x86_64-linux)	10m 8s
runtime5 stack-checks (x86_64-linux)	7m 43s
runtime5 (x86_64-linux)	8m 20s
runtime4 dev (x86_64-linux)	5m 55s
runtime5 frame-pointers irc (x86_64-linux)	7m 36s
runtime5 debug regalloc (aarch64-darwin)	12m 11s
runtime5 regalloc (aarch64-darwin)	9m 30s
runtime4 (aarch64-darwin)	7m 12s
runtime4 Oclassic frame-pointers poll-insertion flambda-invariants (x86_64-linux)	7m 49s
runtime5 address-sanitizer (x86_64-linux)	10m 8s
runtime4 regalloc (x86_64-linux)	10m 28s
runtime5 frame-pointers llvmize-tests (x86_64-linux)	7m 59s
runtime4 address-sanitizer (x86_64-linux)	9m 57s
runtime5 cfg-invariants (x86_64-linux)	7m 31s
runtime5 dwarf-tests (x86_64-linux)	5m 24s
runtime5 regalloc (aarch64-linux)	11m 31s
runtime4 O3 metrics (x86_64-linux)	7m 41s
runtime5 vectorizer (x86_64-linux)	7m 11s
	3h 15m 19s

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