fix(darwin): build broken on darwin since Go 1.18

[orandin]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Bug fix

• What is the current behavior? (You can also link to an open issue here)

$  go version
go version go1.18 darwin/amd64

$ ./utask.sh
# golang.org/x/sys/unix
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/syscall_darwin.1_13.go:29:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.1_13.go:27:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.1_13.go:40:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:28:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:43:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:59:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:75:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:90:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:105:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:121:3: //go:linkname must refer to declared function or variable
../../pkg/mod/golang.org/x/sys@v0.0.0-20201119102817-f84b799fce68/unix/zsyscall_darwin_amd64.go:121:3: too many errors

This was caused by an old version of golang.org/x/sys (mentioned in golang/go#49219).

• What is the new behavior (if this is a feature change)?

Can execute uTask on darwin (MacOS).

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

No.

• Other information:

• x/debug/internal/core: build broken on darwin since at least 2021-10-28 golang/go#49219

[ovh-cds]

CDS Report test#1424.0 ✘

• tests and lint
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