adds experimental sys.Errno to begin decoupling from the syscall package (#1582)

Signed-off-by: Adrian Cole <adrian@tetrate.io>

internal/sysfs/select_unsupported.go

@@ -3,12 +3,12 @@
 package sysfs
 
 import (
-	"syscall"
 	"time"
 
+	"github.com/tetratelabs/wazero/experimental/sys"
 	"github.com/tetratelabs/wazero/internal/platform"
 )
 
 func syscall_select(n int, r, w, e *platform.FdSet, timeout *time.Duration) (int, error) {
-	return -1, syscall.ENOSYS
+	return -1, sys.ENOSYS
 }