domoticz: build with -flto

This makes quite a significant difference to the executable size:

   text    data     bss     dec     hex filename
7921421   87804   31692 8040917  7ab1d5 domoticz
5862321	  86180	  31212	5979713	 5b3e41	domoticz-lto

As an added bonus, it still seems to work.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

utils/domoticz/Makefile

@@ -62,7 +62,8 @@ CMAKE_OPTIONS += \
 	-DUSE_STATIC_OPENZWAVE=no \
 	-DUSE_PYTHON=no
 
-TARGET_CXXFLAGS+=-DWITH_GPIO
+TARGET_CFLAGS+=-flto
+TARGET_CXXFLAGS+=-DWITH_GPIO -flto
 
 define Build/Prepare
 	$(call Build/Prepare/Default)