Add Intel HAXM support to QEMU builder

builder/qemu/builder.go

@@ -25,6 +25,7 @@ var accels = map[string]struct{}{
 	"kvm":  {},
 	"tcg":  {},
 	"xen":  {},
+	"hax":  {},
 }
 
 var netDevice = map[string]bool{
@@ -259,7 +260,7 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 
 	if _, ok := accels[b.config.Accelerator]; !ok {
 		errs = packer.MultiErrorAppend(
-			errs, errors.New("invalid accelerator, only 'kvm', 'tcg', 'xen', or 'none' are allowed"))
+			errs, errors.New("invalid accelerator, only 'kvm', 'tcg', 'xen', 'hax', or 'none' are allowed"))
 	}
 
 	if _, ok := netDevice[b.config.NetDevice]; !ok {

website/source/docs/builders/qemu.html.md

@@ -110,9 +110,9 @@ Linux server and have not enabled X11 forwarding (`ssh -X`).
 ### Optional:
 
 -   `accelerator` (string) - The accelerator type to use when running the VM.
-    This may be `none`, `kvm`, `tcg`, or `xen`. The appropriate software must
-    already been installed on your build machine to use the accelerator you
-    specified. When no accelerator is specified, Packer will try to use `kvm`
+    This may be `none`, `kvm`, `tcg`, `hax`, or `xen`. The appropriate software 
+    must have already been installed on your build machine to use the accelerator 
+    you specified. When no accelerator is specified, Packer will try to use `kvm`
     if it is available but will default to `tcg` otherwise.
 
 -   `boot_command` (array of strings) - This is an array of commands to type