build: include BUILD_VARIANT in PKG_BUILD_DIR

This changes the default PKG_BUILD_DIR to take BUILD_VARIANT into
account (if set), so that packages do not need to manually override
PKG_BUILD_DIR just to handle variants.

This also updates most base packages with variants to use the updated
default PKG_BUILD_DIR.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

package/network/utils/iproute2/Makefile

@@ -19,8 +19,6 @@ PKG_BUILD_DEPENDS:=iptables
 PKG_LICENSE:=GPL-2.0
 PKG_CPE_ID:=cpe:/a:iproute2_project:iproute2
 
-PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(BUILD_VARIANT)/$(PKG_NAME)-$(PKG_VERSION)
-
 include $(INCLUDE_DIR)/kernel.mk
 include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/nls.mk

package/network/utils/iw/Makefile

@@ -15,7 +15,6 @@ PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_SOURCE_URL:=@KERNEL/software/network/iw
 PKG_HASH:=1e38ea794a223525b2ea7fe78fd14f2a56121e62e21ba5f9dbe8c494b35b5c0d
 
-PKG_BUILD_DIR:=$(BUILD_DIR)/iw-$(BUILD_VARIANT)/$(PKG_NAME)-$(PKG_VERSION)
 PKG_MAINTAINER:=Felix Fietkau <nbd@nbd.name>
 PKG_LICENSE:=GPL-2.0
 

package/network/utils/tcpdump/Makefile

@@ -16,7 +16,6 @@ PKG_SOURCE_URL:=http://www.us.tcpdump.org/release/ \
 	http://www.tcpdump.org/release/
 PKG_HASH:=798b3536a29832ce0cbb07fafb1ce5097c95e308a6f592d14052e1ef1505fe79
 
-PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(BUILD_VARIANT)/$(PKG_NAME)-$(PKG_VERSION)
 PKG_BUILD_PARALLEL:=1
 
 PKG_MAINTAINER:=Felix Fietkau <nbd@nbd.name>