tools: Remove -Werror everywhere else

The previous changeset, e4f5949c44 ("tools: Add -Werror by default to all
tools/"), added "-Werror" to CFLAGS in tools/Rules.mk.  Remove it from
everywhere else now it is duplicated.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Acked-by: Daniel P. Smith <dpsmith@apertussolutions.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>

tools/flask/utils/Makefile

@@ -1,7 +1,6 @@
 XEN_ROOT=$(CURDIR)/../../..
 include $(XEN_ROOT)/tools/Rules.mk
 
-CFLAGS += -Werror
 CFLAGS += $(CFLAGS_libxenctrl)
 
 TARGETS := flask-loadpolicy flask-setenforce flask-getenforce flask-label-pci flask-get-bool flask-set-bool