config.mk: Make cc-option create a file under include/generated

Testing for -fstack-usage requires the creation of an output file, which
isn't possible with /dev/null.

Signed-off-by: Tom Rini <trini@ti.com>

config.mk

@@ -108,13 +108,12 @@ HOSTCFLAGS	+= -pedantic
 # only supported compiler options are used
 #
 CC_OPTIONS_CACHE_FILE := $(OBJTREE)/include/generated/cc_options.mk
-
-$(if $(wildcard $(CC_OPTIONS_CACHE_FILE)),,\
-	$(shell mkdir -p $(dir $(CC_OPTIONS_CACHE_FILE))))
+CC_TEST_OFILE := $(OBJTREE)/include/generated/cc_test_file.o
 
 -include $(CC_OPTIONS_CACHE_FILE)
 
-cc-option-sys = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \
+cc-option-sys = $(shell mkdir -p $(dir $(CC_TEST_OFILE)); \
+		if $(CC) $(CFLAGS) $(1) -S -xc /dev/null -o $(CC_TEST_OFILE) \
 		> /dev/null 2>&1; then \
 		echo 'CC_OPTIONS += $(strip $1)' >> $(CC_OPTIONS_CACHE_FILE); \
 		echo "$(1)"; fi)