Added unzip for darwin (#49)

* added unzip for darwin

* add mac builds

* added zip for darwin

__tests__/tool-cache.test.ts

@@ -231,7 +231,9 @@ describe('@actions/tool-cache', function() {
         ]
         await exec.exec(`"${powershellPath}"`, args)
       } else {
-        const zipPath: string = path.join(__dirname, 'externals', 'zip')
+        const zipBin: string =
+          process.platform === 'darwin' ? 'zip-darwin' : 'zip'
+        const zipPath: string = path.join(__dirname, 'externals', zipBin)
         await exec.exec(`"${zipPath}`, [zipFile, '-r', '.'], {cwd: stagingDir})
       }
 
@@ -282,7 +284,9 @@ describe('@actions/tool-cache', function() {
         ]
         await exec.exec(`"${powershellPath}"`, args)
       } else {
-        const zipPath = path.join(__dirname, 'externals', 'zip')
+        const zipBin: string =
+          process.platform === 'darwin' ? 'zip-darwin' : 'zip'
+        const zipPath = path.join(__dirname, 'externals', zipBin)
         await exec.exec(zipPath, [zipFile, '-r', '.'], {cwd: stagingDir})
       }