[#2482] Add condition to use npm.cmd on windows and npm elsewhere (#2484)

Add condition to use npm.cmd on windows and npm elsewhere

Certain gradle tasks do not execute properly on Windows platform,
requiring extension of npm to be specified. Let's fix this issue for 
development on Windows machines.

Author: gekjunxu

build.gradle

@@ -235,19 +235,21 @@ def generateTestReportPortfolio = tasks.register('generateTestReportPortfolio',
     jvmArgs = [ versionJvmArgs ]
 }
 
+def isWindows = System.getProperty('os.name').toLowerCase().contains('windows')
+
 def serveTestReportDefault = tasks.register('serveTestReportDefault', com.github.psxpaul.task.ExecFork) {
     dependsOn generateTestReportDefault
 
     workingDir = './frontend'
-    executable = 'npm'
+    executable = isWindows ? 'npm.cmd' :'npm'
     args = ['run', 'serveTestDefault']
 }
 
 def serveTestReportPortfolio = tasks.register('serveTestReportPortfolio', com.github.psxpaul.task.ExecFork) {
     dependsOn generateTestReportPortfolio
 
     workingDir = './frontend'
-    executable = 'npm'
+    executable = isWindows ? 'npm.cmd' :'npm'
     args = ['run', 'serveTestPortfolio']
 }