Pass down some CFLAGS

Change-Id: I2c69d9ad61137adb82213ad2a4c40e7403a395a5
Avoid -fsanitize=signed-integer-overflow

Change-Id: I1a8ae99401e488e2ece47be4119843945154ef98
fdo#76658 fix bad conversion of old-style UNO service..

in my commit 0394cb37a2d378511f265004b285fd93df37e5ca
"fdo#46808, Convert ui::ImageManager to new style"

Change-Id: I77d3189723403221e7388969b1eb892a244b90af
Signed-off-by: Stephan Bergmann <sbergman@redhat.com>