rules.mk: introduce new variable OUTPUT_DIR

Introduce a new variable OUTPUT_DIR which refers to the parent bin/ directory
without the architecture specific component.

Also construct the BIN_DIR variable based on OUTPUT_DIR now and add both target
and subtarget components to it to prevent different subtargets from
overwriting each others files in bin/.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

rules.mk

@@ -1,5 +1,6 @@
 #
 # Copyright (C) 2006-2010 OpenWrt.org
+# Copyright (C) 2016 LEDE Project
 #
 # This is free software, licensed under the GNU General Public License v2.
 # See /LICENSE for more information.
@@ -54,6 +55,7 @@ CFLAGS:=
 ARCH:=$(subst i486,i386,$(subst i586,i386,$(subst i686,i386,$(call qstrip,$(CONFIG_ARCH)))))
 ARCH_PACKAGES:=$(call qstrip,$(CONFIG_TARGET_ARCH_PACKAGES))
 BOARD:=$(call qstrip,$(CONFIG_TARGET_BOARD))
+SUBTARGET:=$(call qstrip,$(CONFIG_TARGET_SUBTARGET))
 TARGET_OPTIMIZATION:=$(call qstrip,$(CONFIG_TARGET_OPTIMIZATION))
 export EXTRA_OPTIMIZATION:=$(filter-out -fno-plt,$(call qstrip,$(CONFIG_EXTRA_OPTIMIZATION)))
 TARGET_SUFFIX=$(call qstrip,$(CONFIG_TARGET_SUFFIX))
@@ -93,7 +95,8 @@ ifdef CONFIG_MIPS64_ABI
 endif
 
 DL_DIR:=$(if $(call qstrip,$(CONFIG_DOWNLOAD_FOLDER)),$(call qstrip,$(CONFIG_DOWNLOAD_FOLDER)),$(TOPDIR)/dl)
-BIN_DIR:=$(if $(call qstrip,$(CONFIG_BINARY_FOLDER)),$(call qstrip,$(CONFIG_BINARY_FOLDER)),$(TOPDIR)/bin/$(BOARD))
+OUTPUT_DIR:=$(if $(call qstrip,$(CONFIG_BINARY_FOLDER)),$(call qstrip,$(CONFIG_BINARY_FOLDER)),$(TOPDIR)/bin)
+BIN_DIR:=$(OUTPUT_DIR)/targets/$(BOARD)/$(SUBTARGET)
 INCLUDE_DIR:=$(TOPDIR)/include
 SCRIPT_DIR:=$(TOPDIR)/scripts
 BUILD_DIR_BASE:=$(TOPDIR)/build_dir