Fix build script not exiting on msbuild failure.

scripts/build.ps1

@@ -105,6 +105,9 @@ Pop-Location
 if($Compile) {
     Push-Location -Path $launcher
     msbuild CmderLauncher.vcxproj /p:configuration=Release
+    if ($LastExitCode -ne 0) {
+        throw "msbuild failed to build the executable."
+    }
     Pop-Location
 } else {
     Write-Warning "You are not building a launcher, Use -Compile"