[CI] Expose linux and windows machine types through gke_cluster

This enables using different instance types for different clusters where we
might have different quota.

Reviewers: dschuff, lnihlen, Keenuts, cmtice, gburgessiv

Reviewed By: lnihlen

Pull Request: #444

Author: boomanaiden154

premerge/gke_cluster/main.tf

@@ -37,7 +37,7 @@ resource "google_container_node_pool" "llvm_premerge_linux" {
   }
 
   node_config {
-    machine_type = "n2-standard-64"
+    machine_type = var.linux_machine_type
     taint {
       key    = "premerge-platform"
       value  = "linux"
@@ -71,7 +71,7 @@ resource "google_container_node_pool" "llvm_premerge_windows" {
   # We do not set a taint for the windows nodes as kubernetes by default sets
   # a node.kubernetes.io/os taint for windows nodes.
   node_config {
-    machine_type = "n2-standard-32"
+    machine_type = var.windows_machine_type
     labels = {
       "premerge-platform" : "windows"
     }

premerge/gke_cluster/variables.tf

@@ -7,3 +7,13 @@ variable "region" {
   description = "The region to run the cluster in"
   type        = string
 }
+
+variable "linux_machine_type" {
+  description = "The type of machine to use for Linux instances"
+  type        = string
+}
+
+variable "windows_machine_type" {
+  description = "The type of machine to use for Windows instances"
+  type        = string
+}

premerge/main.tf

@@ -49,6 +49,8 @@ module "premerge_cluster_us_central" {
   source       = "./gke_cluster"
   cluster_name = "llvm-premerge-prototype"
   region       = "us-central1-a"
+  linux_machine_type   = "n2-standard-64"
+  windows_machine_type = "n2-standard-32"
 }
 
 # TODO(boomanaiden154): Remove these statements after the changes have been