Bug 1360819 - Do not show a console on Windows when launching the pingsender; r=Dexter

MozReview-Commit-ID: 54TBiNMFcWM

--HG--
extra : rebase_source : eb0eb6005608f31b8ec765c572b6b789ff3ec10a

toolkit/components/telemetry/pingsender/pingsender_win.cpp

@@ -8,6 +8,8 @@
 #include <windows.h>
 #include <wininet.h>
 
+#pragma comment(linker, "/SUBSYSTEM:windows /ENTRY:mainCRTStartup")
+
 namespace PingSender {
 
 using std::string;