tweak cmake guard

Author: kilograham

pico_w/wifi/CMakeLists.txt

@@ -20,8 +20,8 @@ else()
     add_subdirectory_exclude_platforms(http_client)
     add_subdirectory_exclude_platforms(mqtt)
 
-    if (NOT PICO_MBEDTLS_PATH)
-        message("Skipping some examples as PICO_MBEDTLS_PATH is not defined")
+    if (NOT TARGET pico_mbed_tls)
+        message("Skipping tls_client and ota_update examples as Mbed TLS is not available")
     else()
         add_subdirectory_exclude_platforms(tls_client)
         add_subdirectory_exclude_platforms(ota_update rp2040)