toolchain: also setup kernel headers when ext toolchain is used

Provide kernel headers when ext toolchain is used, so we can compile
packages which need them.

Makefile

@@ -196,7 +196,7 @@ PREFERRED_LIB_FLAGS:=--enable-static --enable-shared
 ifeq ($(BR2_TOOLCHAIN_SOURCE),y)
 BASE_TARGETS:=uclibc-configured binutils cross_compiler uclibc-target-utils kernel-headers
 else
-BASE_TARGETS:=uclibc
+BASE_TARGETS:=uclibc kernel-headers
 endif
 TARGETS:=
 

toolchain/Config.in.2

@@ -1,7 +1,8 @@
 #
 
-if BR2_TOOLCHAIN_SOURCE
 source "toolchain/kernel-headers/Config.in"
+
+if BR2_TOOLCHAIN_SOURCE
 source "toolchain/uClibc/Config.in"
 source "toolchain/binutils/Config.in"
 source "toolchain/gcc/Config.in"

toolchain/kernel-headers/kernel-headers.mk

@@ -6,13 +6,9 @@
 # by a 'make clean' so don't put anything sacred in here...
 #
 #############################################################
-ifeq ($(BR2_TOOLCHAIN_EXTERNAL),y)
-DEFAULT_KERNEL_HEADERS:=$(strip $(subst ",, $(BR2_LINUX26_VERSION)))
-#"))
-else
+
 DEFAULT_KERNEL_HEADERS:=$(strip $(subst ",, $(BR2_DEFAULT_KERNEL_HEADERS)))
 #"))
-endif
 
 LINUX_HEADERS_SITE:=127.0.0.1
 LINUX_HEADERS_SOURCE:=unspecified-kernel-headers