guard negative operands in MathLib::value shift operators #20142

Job	Run time
build_make (ubuntu:25.10)	4m 49s
build_make (alpine:3.23)	5m 54s
build_cmake (alpine:3.23, false, false)	4m 17s
build_make (ubuntu:24.04)	4m 17s
build_cmake (ubuntu:24.04, true, true)	4m 58s
build_cmake (ubuntu:25.10, true, true)	5m 12s
	29m 27s

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