Fix length function to measure code units #35

Job	Run time
arm (arm32v7)	9m 40s
i386	9m 54s
arm (arm64v8)	8m 42s
darwin_arm (self-hosted, macOS, ARM64, 8.10.7)	1h 0m 14s
build (ubuntu-latest, 8.6, 3.8.1.0)	11m 45s
darwin_arm (self-hosted, macOS, ARM64, 9.2.8)	27m 57s
build (ubuntu-latest, 8.8, 3.8.1.0)	12m 3s
darwin_arm (self-hosted, macOS, ARM64, 9.4.7)	23m 36s
emulated (s390x)	22m 51s
build (ubuntu-latest, 8.10, 3.8.1.0)	10m 9s
freebsd (self-hosted, FreeBSD, X64, 9.4.8)	5m 52s
emulated (ppc64le)	19m 43s
build (ubuntu-latest, 9.0, 3.8.1.0)	13m 16s
freebsd (self-hosted, FreeBSD, X64, 9.6.4)	6m 25s
build (ubuntu-latest, 9.2, 3.8.1.0)	9m 30s
build (ubuntu-latest, 9.4, 3.8.1.0)	9m 26s
build (ubuntu-latest, 9.6, 3.8.1.0)	9m 30s
build (ubuntu-latest, 9.8, 3.8.1.0)	8m 29s
build (macOS-12, 9.4, 3.8.1.0)	1h 19m 53s
build (macOS-12, 9.6, 3.8.1.0)	49m 6s
build (windows-latest, 9.4, 3.8.1.0)	48m 47s
build (windows-latest, 9.6, 3.8.1.0)	51m 37s
	8h 28m 25s

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