fork: fix return value not being set in child #2148

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	54s
call-ci / build (armv7a9-zynq7000-qemu)	53s
call-ci / build (armv7a9-zynq7000-zedboard)	54s
call-ci / build (armv7a9-zynq7000-zturn)	52s
call-ci / build (armv7m4-stm32l4x6-nucleo)	52s
call-ci / build (armv7m7-imxrt105x-evk)	43s
call-ci / build (armv7m7-imxrt106x-evk)	43s
call-ci / build (armv7m7-imxrt117x-evk)	52s
call-ci / build (armv8r52-mps3an536-qemu)	53s
call-ci / build (armv8m33-mcxn94x-frdm)	53s
call-ci / build (host-generic-pc)	52s
call-ci / build (ia32-generic-pc)	53s
call-ci / build (ia32-generic-qemu)	53s
call-ci / build (riscv64-generic-qemu)	42s
call-ci / build (riscv64-generic-spike)	39s
call-ci / build (sparcv8leon-generic-qemu)	51s
call-ci / build (sparcv8leon-gr712rc-board)	1s
call-ci / build (sparcv8leon-gr716-mimas)	53s
call-ci / build (sparcv8leon-gr716-mini)	23s
call-ci / test HW	0s
call-ci / test EMU	0s
call-ci / tests-summary	9s
call-ci / send-notification	0s
	14m 45s

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