fix mbox numbering #151

Job	Run time
build-linux (mnfst, imx8 imx8x imx8m imx8ulp)	3m 8s
build-windows (imx8 imx8x imx8m imx8ulp)	5m 23s
build-linux (mnfst, mtl)	3m 18s
build-windows (mtl)	5m 34s
build-linux (mnfst, lnl)	3m 16s
build-windows (tgl tgl-h)	5m 27s
build-linux (mnfst, tgl tgl-h)	2m 57s
build-windows (-d, mtl)	5m 26s
build-linux (zmain, imx8 imx8x imx8m imx8ulp)	3m 51s
build-linux (zmain, mtl)	3m 55s
LP64-WIP	2m 55s
build-linux (zmain, lnl)	3m 53s
build-linux (zmain, tgl tgl-h)	3m 32s
build-linux (-d, mnfst, mtl)	3m 16s
manifest-check	42s
build-linux (mnfst, --all)	3m 5s
compare-linux-win	14s
	59m 52s

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