Allow compiling without nvidia integration

nvidia library use of dynamic library seems to conflict with alpine and
musl based OSes.  This adds a `nonvidia` tag to allow compiling nomad
for alpine images.

The nomad releases currently only support glibc based OS environments,
so we default to compiling with nvidia.

drivers/docker/driver.go

@@ -18,7 +18,6 @@ import (
 	multierror "github.com/hashicorp/go-multierror"
 	plugin "github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/nomad/client/taskenv"
-	"github.com/hashicorp/nomad/devices/gpu/nvidia"
 	"github.com/hashicorp/nomad/drivers/docker/docklog"
 	"github.com/hashicorp/nomad/drivers/shared/eventer"
 	nstructs "github.com/hashicorp/nomad/nomad/structs"
@@ -56,6 +55,9 @@ var (
 	// taskHandleVersion is the version of task handle which this driver sets
 	// and understands how to decode driver state
 	taskHandleVersion = 1
+
+	// Nvidia-container-runtime environment variable names
+	nvidiaVisibleDevices = "NVIDIA_VISIBLE_DEVICES"
 )
 
 type Driver struct {
@@ -684,7 +686,7 @@ func (d *Driver) createContainerConfig(task *drivers.TaskConfig, driverConfig *T
 		PidsLimit: driverConfig.PidsLimit,
 	}
 
-	if _, ok := task.DeviceEnv[nvidia.NvidiaVisibleDevices]; ok {
+	if _, ok := task.DeviceEnv[nvidiaVisibleDevices]; ok {
 		if !d.gpuRuntime {
 			return c, fmt.Errorf("requested docker-runtime %q was not found", d.config.GPURuntimeName)
 		}

helper/pluginutils/catalog/register_linux.go

@@ -1,7 +1,6 @@
 package catalog
 
 import (
-	"github.com/hashicorp/nomad/devices/gpu/nvidia"
 	"github.com/hashicorp/nomad/drivers/rkt"
 )
 
@@ -10,5 +9,4 @@ import (
 // register_XXX.go file.
 func init() {
 	RegisterDeferredConfig(rkt.PluginID, rkt.PluginConfig, rkt.PluginLoader)
-	Register(nvidia.PluginID, nvidia.PluginConfig)
 }

helper/pluginutils/catalog/register_nvidia_linux.go

@@ -0,0 +1,14 @@
+// +build !nonvidia
+
+package catalog
+
+import (
+	"github.com/hashicorp/nomad/devices/gpu/nvidia"
+)
+
+// This file is where all builtin plugins should be registered in the catalog.
+// Plugins with build restrictions should be placed in the appropriate
+// register_XXX.go file.
+func init() {
+	Register(nvidia.PluginID, nvidia.PluginConfig)
+}