CMake: use functions instead of macros

Reduces issues with vars leaking into the parent scope.

GNUmakefile

@@ -124,12 +124,12 @@ all: FORCE
 	@echo
 	@echo Configuring Blender ...
 
-	# if test ! -f $(BUILD_DIR)/CMakeCache.txt ; then \
-	# 	$(CMAKE_CONFIG); \
-	# fi
+#	# if test ! -f $(BUILD_DIR)/CMakeCache.txt ; then \
+#	# 	$(CMAKE_CONFIG); \
+#	# fi
 	
-	# do this always incase of failed initial build, could be smarter here...
-	$(CMAKE_CONFIG)
+#	# do this always incase of failed initial build, could be smarter here...
+	@$(CMAKE_CONFIG)
 
 	@echo
 	@echo Building Blender ...