Suppress unused variable warnings in CFLAGS to reduce noise when NO_STDOUT_DEBUG is enabled

wpa_supplicant/.config

@@ -249,6 +249,9 @@ CONFIG_CTRL_IFACE=y
 # if debugging code is not needed. The size reduction can be around 35%
 # (e.g., 90 kB).
 CONFIG_NO_STDOUT_DEBUG=y
+# With NO_STDOUT_DEBUG wpa_printf() expands to nothing, so variables and
+# helpers used only for debug output become "unused". Silence that noise.
+CFLAGS += -Wno-unused-variable -Wno-unused-but-set-variable -Wno-unused-function
 
 # Remove WPA support, e.g., for wired-only IEEE 802.1X supplicant, to save
 # 35-50 kB in code size.