fix: update golang.org/x/sys to support go1.18 build

[ag9920]

Currently go build/test will fail if you're using Golang 1.18. Here's the output:

# golang.org/x/sys/unix
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:28:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:43:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:59:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:75:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:90:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:105:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:121:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:136:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:151:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:166:3: //go:linkname must refer to declared function or variable
../../../../pkg/mod/golang.org/x/sys@v0.0.0-20181221143128-b4a75ba826a6/unix/zsyscall_darwin_amd64.go:166:3: too many errors
FAIL    github.com/xujiajun/nutsdb [build failed]

This was caused by an old version of golang.org/x/sys (mentioned in this issue).

This PR simply update golang.org/x/sys to support go1.18. I've already test it locally.