Add check if mpm already exists

Author: Vahila

src/mpm.ts

@@ -4,6 +4,7 @@ import * as exec from "@actions/exec";
 import * as tc from "@actions/tool-cache";
 import {rmRF} from "@actions/io";
 import * as path from "path";
+import * as fs from 'fs';
 import * as matlab from "./matlab";
 import properties from "./properties.json";
 
@@ -37,15 +38,21 @@ export async function setup(platform: string, architecture: string): Promise<str
         return Promise.reject(Error("Unable to find runner temporary directory."));
     }
     let mpmDest = path.join(runner_temp, `mpm${ext}`);
-    let mpm: string = await tc.downloadTool(mpmUrl, mpmDest);
+    if (!fs.existsSync(mpmDest)){
+        let mpm: string = await tc.downloadTool(mpmUrl, mpmDest);
 
-    if (platform !== "win32") {
-        const exitCode = await exec.exec(`chmod +x "${mpm}"`);
-        if (exitCode !== 0) {
-            return Promise.reject(Error("Unable to set up mpm."));
+        if (platform !== "win32") {
+            const exitCode = await exec.exec(`chmod +x "${mpm}"`);
+            if (exitCode !== 0) {
+                return Promise.reject(Error("Unable to set up mpm."));
+            }
         }
+
+        return mpm;
+    }
+    else{
+        return mpmDest 
     }
-    return mpm
 }
 
 export async function install(mpmPath: string, release: matlab.Release, products: string[], destination: string) {