tools thermal tmon: Allow overriding CFLAGS assignments

So that the user can provide, e.g. distro package alternative values.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Herton Krzesinski  <herton@redhat.com>
Cc: Markus Mayer <mmayer@broadcom.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Link: http://lkml.kernel.org/r/20181212102537.25902-3-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/thermal/tmon/Makefile

@@ -6,13 +6,13 @@ VERSION = 1.0
 
 BINDIR=usr/bin
 WARNFLAGS=-Wall -Wshadow -W -Wformat -Wimplicit-function-declaration -Wimplicit-int
-CFLAGS+= -O1 ${WARNFLAGS}
+override CFLAGS+= -O1 ${WARNFLAGS}
 # Add "-fstack-protector" only if toolchain supports it.
-CFLAGS+= $(call cc-option,-fstack-protector)
+override CFLAGS+= $(call cc-option,-fstack-protector-strong)
 CC?= $(CROSS_COMPILE)gcc
 PKG_CONFIG?= pkg-config
 
-CFLAGS+=-D VERSION=\"$(VERSION)\"
+override CFLAGS+=-D VERSION=\"$(VERSION)\"
 LDFLAGS+=
 TARGET=tmon
 
@@ -29,7 +29,7 @@ TMON_LIBS += $(shell $(PKG_CONFIG) --libs $(STATIC) panelw ncursesw 2> /dev/null
 		     $(PKG_CONFIG) --libs $(STATIC) panel ncurses 2> /dev/null || \
 		     echo -lpanel -lncurses)
 
-CFLAGS    += $(shell $(PKG_CONFIG) --cflags $(STATIC) panelw ncursesw 2> /dev/null || \
+override CFLAGS += $(shell $(PKG_CONFIG) --cflags $(STATIC) panelw ncursesw 2> /dev/null || \
 		     $(PKG_CONFIG) --cflags $(STATIC) panel ncurses 2> /dev/null)
 
 OBJS = tmon.o tui.o sysfs.o pid.o