Followup to #8731: use isSplittedVarDeclEq() #20413

Job	Run time
build_make (ubuntu:24.04)	3m 29s
build_cmake (alpine:3.23, false, false)	4m 29s
build_make (alpine:3.23)	6m 10s
build_cmake (ubuntu:24.04, true, true)	6m 54s
build_make (ubuntu:25.10)	9m 43s
build_cmake (ubuntu:25.10, true, true)	6m 7s
	36m 52s

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