few assorted changes in preparation syz-agent binary #18336

Job	Run time
race	7m 0s
old	7m 11s
build	3m 27s
gvisor	3m 39s
arch (presubmit_arch_linux)	10m 55s
aux	3m 53s
dashboard	2m 32s
race_dashboard	3m 59s
arch (presubmit_arch_freebsd)	5m 57s
arch (presubmit_arch_executor)	3m 13s
arch (presubmit_arch_windows)	3m 35s
arch (presubmit_arch_openbsd)	3m 54s
arch (presubmit_arch_netbsd)	3m 48s
arch (presubmit_arch_darwin)	3m 19s
	1h 6m 22s

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