[make] add new TESTANDREPLACEFILE macro

Split the MAKECONFIGHEADER macro into the part that generates
the header and the part that tests if you should replace the
target file with the generated one.

make/macros.mk

@@ -11,11 +11,27 @@ COMMA := ,
 SPACE :=
 SPACE +=
 
+# test if two files are different, replacing the first
+# with the second if so
+# args: $1 - temporary file to test
+#       $2 - file to replace
+define TESTANDREPLACEFILE
+	if [ -f "$2" ]; then \
+		if cmp "$1" "$2"; then \
+			rm -f $1; \
+		else \
+			mv $1 $2; \
+		fi \
+	else \
+		mv $1 $2; \
+	fi
+endef
+
 # generate a header file at $1 with an expanded variable in $2
 define MAKECONFIGHEADER
-	@$(MKDIR)
-	@echo generating $1
-	@rm -f $1.tmp; \
+	$(MKDIR); \
+	echo generating $1; \
+	rm -f $1.tmp; \
 	LDEF=`echo $1 | tr '/\\.-' '_'`; \
 	echo \#ifndef __$${LDEF}_H > $1.tmp; \
 	echo \#define __$${LDEF}_H >> $1.tmp; \
@@ -23,13 +39,5 @@ define MAKECONFIGHEADER
 		echo "#define $$d" | sed "s/=/\ /g;s/-/_/g;s/\//_/g;s/\./_/g;s/\//_/g" >> $1.tmp; \
 	done; \
 	echo \#endif >> $1.tmp; \
-	if [ -f "$1" ]; then \
-		if cmp "$1.tmp" "$1"; then \
-			rm -f $1.tmp; \
-		else \
-			mv $1.tmp $1; \
-		fi \
-	else \
-		mv $1.tmp $1; \
-	fi
+	$(call TESTANDREPLACEFILE,$1.tmp,$1)
 endef