x/benchmarks/sweet/cmd/sweet: new dependencies mean tests can't build on plan9 or js/wasm #74149
Description
CL 679675 seems to have added some non-portable dependencies which break the x_benchmarks repo builders on plan9 and js/wasm.
On builder x_benchmarks-gotip-plan9-arm for example, we have:
FAIL golang.org/x/benchmarks/sweet/cmd/sweet [build failed]
# go.chromium.org/luci/cipd/client/cipd/fs
../gopath/pkg/mod/go.chromium.org/luci@v0.0.0-20250606083430-318ed8f4881d/cipd/client/cipd/fs/errs.go:44:15: undefined: syscall.Errno
../gopath/pkg/mod/go.chromium.org/luci@v0.0.0-20250606083430-318ed8f4881d/cipd/client/cipd/fs/fs_posix.go:34:24: undefined: syscall.ENOTEMPTY
ok golang.org/x/benchmarks/sweet/common 0.872s
# github.com/danjacques/gofslock/fslock
../gopath/pkg/mod/github.com/danjacques/gofslock@v0.0.0-20240212154529-d899e02bfe22/fslock/lock_unix.go:63:29: undefined: syscall.Stat_t
../gopath/pkg/mod/github.com/danjacques/gofslock@v0.0.0-20240212154529-d899e02bfe22/fslock/lock_unix.go:96:12: undefined: flockLock
../gopath/pkg/mod/github.com/danjacques/gofslock@v0.0.0-20240212154529-d899e02bfe22/fslock/lock_unix.go:157:42: undefined: syscall.SYS_FCNTL
../gopath/pkg/mod/github.com/danjacques/gofslock@v0.0.0-20240212154529-d899e02bfe22/fslock/lock_unix.go:157:80: undefined: syscall.F_SETFD
../gopath/pkg/mod/github.com/danjacques/gofslock@v0.0.0-20240212154529-d899e02bfe22/fslock/lock_unix.go:157:108: undefined: syscall.Errno
# go.chromium.org/luci/common/system/unixsock
../gopath/pkg/mod/go.chromium.org/luci@v0.0.0-20250606083430-318ed8f4881d/common/system/unixsock/unixsock.go:62:24: undefined: syscall.RawSockaddrUnix
and on builder x_benchmarks-gotip-js-wasm we have
FAIL golang.org/x/benchmarks/sweet/cmd/sweet [build failed]
# github.com/danjacques/gofslock/fslock
../gopath/pkg/mod/github.com/danjacques/gofslock@v0.0.0-20240212154529-d899e02bfe22/fslock/lock_unix.go:96:12: undefined: flockLock
ok golang.org/x/benchmarks/sweet/common 0.220s
# go.chromium.org/luci/common/system/unixsock
../gopath/pkg/mod/go.chromium.org/luci@v0.0.0-20250606083430-318ed8f4881d/common/system/unixsock/unixsock.go:62:24: undefined: syscall.RawSockaddrUnix