Add comment on when to use BUILD_DIR vs PROJECT_BUILD_DIR

package/Makefile.in

@@ -68,8 +68,11 @@ ifeq ($(DL_DIR),)
 DL_DIR:=$(BASE_DIR)/dl
 endif
 #PATCH_DIR=$(BASE_DIR)/sources/patches
+
+# All non-configurable packages should be built in BUILD_DIR
 BUILD_DIR:=$(BASE_DIR)/$(TOPDIR_PREFIX)build_$(ARCH)$(ARCH_FPU_SUFFIX)$(TOPDIR_SUFFIX)
 
+# All configurable packages (like Busybox,Linux etc) should be built in PROJECT_BUILD_DIR
 PROJECT_BUILD_DIR:=$(BASE_DIR)/$(TOPDIR_PREFIX)project_build_$(ARCH)$(ARCH_FPU_SUFFIX)$(TOPDIR_SUFFIX)/$(PROJECT)
 BINARIES_DIR:=$(BASE_DIR)/binaries/$(PROJECT)
 TARGET_DIR:=$(PROJECT_BUILD_DIR)/root