WIP: add $HOSTTYPE and $OSTYPE

Bash has those implicit variables set. Do you think it's worth having
them in here as well? I don't have the full mapping but happy to keep
digging.

interp/api.go

@@ -14,6 +14,7 @@ import (
  "math/rand"
  "os"
  "path/filepath"
+ "runtime"
  "strconv"
  "sync"
  "time"
@@ -617,10 +618,23 @@ func (r *Runner) Reset() {
  r.setVarString("IFS", " \t\n")
  r.setVarString("OPTIND", "1")
 
+ r.setVarString("HOSTTYPE", goos2hosttype[runtime.GOOS])
+ r.setVarString("OSTYPE", goarch2ostype[runtime.GOARCH])
+
  r.dirStack = append(r.dirStack, r.Dir)
  r.didReset = true
 }
 
+// FIXME: add more goarch and goos
+var goos2hosttype = map[string]string{
+ "linux": "linux-gnu",
+ "darwin": "darwin17.7.0",
+}
+var goarch2ostype = map[string]string{
+ "386": "i686",
+ "amd64": "x86_64",
+}
+
 // exitStatus is a non-zero status code resulting from running a shell node.
 type exitStatus uint8