Disable stack protection

The stack protection is incompatible with --no-undefined because none of
the libraries we link with contain the canary symbol.

cores/Tuprules.tup

@@ -31,4 +31,8 @@ PKG_DEPENDS += \
 LINK_T = $(TUP_CWD)/link.T
 DEFINES += -fPIC -D__LIBRETRO__ -DFRONTEND_SUPPORTS_RGB565
 DEFINES += -DGIT_VERSION=\"$(GIT_VERSION)\"
+
+CFLAGS += -fno-stack-protector
+CXXFLAGS += -fno-stack-protector
+
 NO_UNDEFINED = --no-undefined