dashboard/config/linux: enable BB descriptors #19059

Job	Run time
race	7m 18s
aux	4m 38s
build	3m 10s
dashboard	2m 29s
old	6m 56s
race_dashboard	3m 28s
gvisor	4m 12s
arch (presubmit_arch_windows)	3m 41s
arch (presubmit_arch_executor)	2m 52s
arch (presubmit_arch_netbsd)	3m 55s
arch (presubmit_arch_darwin)	3m 57s
arch (presubmit_arch_freebsd)	6m 25s
arch (presubmit_arch_linux)	10m 38s
arch (presubmit_arch_openbsd)	3m 23s
	1h 7m 2s

Provide feedback