Repro instructions for QEMU SIGRTMIN patch

repro.log

$ go version
go version go1.13.7 linux/amd64
$ env GOOS=linux GOARCH=arm64 go build test.go
$ aarch64-linux-user/qemu-aarch64 ./test
fatal error: sigaction failed

runtime stack:
runtime.throw(0xd60c0, 0x10)
        ~/code/go/src/runtime/panic.go:774 +0x54
runtime.sysSigaction.func1()
        ~/code/go/src/runtime/os_linux.go:446 +0x34
runtime.sysSigaction(0x400000003f, 0x40007ff688, 0x0)
        ~/code/go/src/runtime/os_linux.go:445 +0x74
runtime.sigaction(0x400000003f, 0x40007ff688, 0x0)
        ~/code/go/src/runtime/cgo_sigaction.go:32 +0x48
runtime.setsig(0x3f, 0x4a860)
        ~/code/go/src/runtime/os_linux.go:395 +0xa4
runtime.initsig(0x4000029e00)
        ~/code/go/src/runtime/signal_unix.go:113 +0x188
runtime.mstartm0()
        ~/code/go/src/runtime/proc.go:1225 +0x44
runtime.mstart1()
        ~/code/go/src/runtime/proc.go:1197 +0xc4
runtime.mstart()
        ~/code/go/src/runtime/proc.go:1167 +0x60

goroutine 1 [runnable]:
runtime.main()
        ~/code/go/src/runtime/proc.go:113
runtime.goexit()
        ~/code/go/src/runtime/asm_arm64.s:1128 +0x4

test.go

package main 

import (
	"fmt"
)

func main() {
	fmt.Println("Hello World")
}