Followup to #8731: use isSplittedVarDeclEq() #20416

Job	Run time
build_cmake (ubuntu:24.04, true, true)	2m 57s
build_cmake (ubuntu:25.10, true, true)	5m 48s
build_make (alpine:3.23)	3m 18s
build_make (ubuntu:25.10)	3m 31s
build_make (ubuntu:24.04)	3m 6s
build_cmake (alpine:3.23, false, false)	4m 50s
	23m 30s

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