v8: use primordials in startup_snapshot.js #1881

Job	Run time
Build slim tarball	1m 29s
aarch64-linux: with shared libraries	24m 44s
aarch64-darwin: with shared libraries	26m 37s
x86_64-darwin: with shared libraries	42m 49s
x86_64-linux: with shared libraries	30m 14s
	2h 5m 53s

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