(cmake) default TLS back to mbedtls on Windows Universal Platform

CMakeLists.txt

@@ -123,6 +123,11 @@ if (USE_TLS)
       if (NOT USE_MBED_TLS AND NOT USE_OPEN_SSL) # unless we want something else
         set(USE_SECURE_TRANSPORT ON)
       endif()
+    # default to mbedtls on uwp (universal windows platform) if nothing is configured
+    elseif (${CMAKE_SYSTEM_NAME} MATCHES "WindowsStore")
+      if (NOT USE_OPEN_SSL) # unless we want something else
+        set(USE_MBED_TLS ON)
+      endif()
     else() # default to OpenSSL on all other platforms
       if (NOT USE_MBED_TLS) # Unless mbedtls is requested
         set(USE_OPEN_SSL ON)