provisioner/shell: quote PACKER env vars [GH-1565]

provisioner/shell/provisioner.go

@@ -230,8 +230,8 @@ func (p *Provisioner) Provision(ui packer.Ui, comm packer.Communicator) error {
 
 	// Build our variables up by adding in the build name and builder type
 	envVars := make([]string, len(p.config.Vars)+2)
-	envVars[0] = "PACKER_BUILD_NAME=" + p.config.PackerBuildName
-	envVars[1] = "PACKER_BUILDER_TYPE=" + p.config.PackerBuilderType
+	envVars[0] = fmt.Sprintf("PACKER_BUILD_NAME='%s'", p.config.PackerBuildName)
+	envVars[1] = fmt.Sprintf("PACKER_BUILDER_TYPE='%s'", p.config.PackerBuilderType)
 	copy(envVars[2:], p.config.Vars)
 
 	for _, path := range scripts {