sub-process: use gentle handshake to avoid die() on startup failure #28134

Job	Run time
config	8s
fuzz smoke test	1m 36s
win build	5m 2s
rust-analysis	1m 32s
win+Meson build	4m 14s
sparse	3m 39s
documentation	7m 9s
static-analysis	6m 12s
osx-clang (macos-14)	49m 46s
win+VS build	0s
osx-reftable (macos-14)	52m 35s
osx-meson (macos-14)	52m 35s
linux-meson (ubuntu:rolling)	21m 30s
osx-gcc (macos-14)	52m 35s
linux-asan-ubsan (ubuntu:rolling)	43m 3s
linux-reftable-leaks (ubuntu:rolling)	47m 15s
debian-11 (debian:11)	21m 49s
linux-musl-meson (alpine:latest)	21m 22s
linux-reftable (ubuntu:rolling)	17m 38s
linux32 (i386/ubuntu:focal)	43m 14s
linux-sha256 (ubuntu:rolling)	29m 21s
linux-leaks (ubuntu:rolling)	38m 12s
linux-TEST-vars (ubuntu:20.04)	17m 10s
fedora-breaking-changes-meson (fedora:latest)	18m 18s
almalinux-8 (almalinux:8)	23m 1s
linux-breaking-changes (ubuntu:rolling)	24m 44s
win+VS test	0s
win+Meson test (8)	9m 44s
win+Meson test (2)	26m 49s
win+Meson test (0)	8m 33s
win+Meson test (6)	14m 19s
win+Meson test (9)	7m 5s
win+Meson test (5)	8m 14s
win+Meson test (3)	9m 31s
win+Meson test (1)	9m 7s
win+Meson test (4)	7m 39s
win+Meson test (7)	6m 50s
win test (3)	14m 35s
win test (0)	11m 29s
win test (8)	5s
win test (5)	11m 46s
win test (2)	8m 8s
win test (1)	7m 26s
win test (4)	12m 32s
win test (6)	7m 22s
win test (9)	6m 0s
win test (7)	6m 43s
	13h 17m 37s

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