vela: Modify CFLAGS for mlw_codec makefile

Fix signed/unsigned warning
Removed from README.md as it adds no value. The standalone tool is not
expected to be used by customers.

Signed-off-by: Michael McGeagh <michael.mcgeagh@arm.com>
Change-Id: I09034478a14c37d30874d5182a096591dfdd6eb2
diff --git a/ethosu/mlw_codec/makefile b/ethosu/mlw_codec/makefile
index 68eb0d9..aa214f9 100644
--- a/ethosu/mlw_codec/makefile
+++ b/ethosu/mlw_codec/makefile
@@ -20,7 +20,8 @@
 
 UNAME=$(shell uname -o)
 
-CFLAGS=-Wall -Werror -Wno-unused-function -Wno-unused-variable
+CFLAGS=-Wall -Werror -Wno-unused-variable
+CFLAGS+=-fwrapv -fstack-protector-strong -flto -fuse-linker-plugin -ffat-lto-objects
 
 ifeq ($(DEBUG),1)
     CFLAGS+=-g -O0 -DDEBUG