kola/azure/options: determine default machine size based on architecture

Now that we can build aarch64 Azure images, drop the default machine
size from the Cobra command flags and determine it dynamically based on
the architecture, consistent with other cloud platforms.

Author: marmijo

mantle/cmd/kola/options.go

@@ -99,7 +99,7 @@ func init() {
 	sv(&kola.AzureOptions.Sku, "azure-sku", "alpha", "Azure image sku/channel (default \"alpha\"")
 	sv(&kola.AzureOptions.Version, "azure-version", "", "Azure image version")
 	sv(&kola.AzureOptions.Location, "azure-location", "westus", "Azure location (default \"westus\"")
-	sv(&kola.AzureOptions.Size, "azure-size", "Standard_D2s_v3", "Azure machine size (default \"Standard_D2s_v3\")")
+	sv(&kola.AzureOptions.Size, "azure-size", "", "Azure machine size")
 	sv(&kola.AzureOptions.AvailabilityZone, "azure-availability-zone", "1", "Azure Availability Zone (default \"1\")")
 
 	// do-specific options
@@ -233,6 +233,17 @@ func syncOptionsImpl(useCosa bool) error {
 		fmt.Printf("Using %s instance type\n", kola.AWSOptions.InstanceType)
 	}
 
+	// Choose an appropriate Azure instance type (size) for the target architecture
+	if kolaPlatform == "azure" && kola.AzureOptions.Size == "" {
+		switch kola.Options.CosaBuildArch {
+		case "x86_64":
+			kola.AzureOptions.Size = "Standard_D2s_v3"
+		case "aarch64":
+			kola.AzureOptions.Size = "Standard_D2ps_v5"
+		}
+		fmt.Printf("Using %s size\n", kola.AzureOptions.Size)
+	}
+
 	// Choose an appropriate GCP instance type for the target architecture
 	if kolaPlatform == "gcp" && kola.GCPOptions.MachineType == "" {
 		switch kola.Options.CosaBuildArch {