[source] include/toplevel.mk: Add xconfig target

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/23dd6db2ea6d783c16bf10b43c23478b7f26723d

commit 23dd6db2ea6d783c16bf10b43c23478b7f26723d
Author: Alif M. Ahmad <alive4ever at live.com>
AuthorDate: Sun Jul 23 03:08:56 2017 +0000

    include/toplevel.mk: Add xconfig target
    
    Add xconfig target to include/toplevel.mk, so that ``make xconfig`` can
    be invoked from $TOPDIR to use Qt based configuration tool to prepare
    .config file.
    
    The qconf related sources are taken from linux 4.9.13 archive.
    
    Signed-off-by: Alif M. Ahmad <alive4ever at live.com>
---
 include/toplevel.mk | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/toplevel.mk b/include/toplevel.mk
index 658eb4c..3f5a750 100644
--- a/include/toplevel.mk
+++ b/include/toplevel.mk
@@ -104,6 +104,9 @@ scripts/config/mconf:
 
 $(eval $(call rdep,scripts/config,scripts/config/mconf))
 
+scripts/config/qconf:
+	@$(_SINGLE)$(SUBMAKE) -s -C scripts/config qconf CC="$(HOSTCC_WRAPPER)"
+
 scripts/config/conf:
 	@$(_SINGLE)$(SUBMAKE) -s -C scripts/config conf CC="$(HOSTCC_WRAPPER)"
 
@@ -136,6 +139,12 @@ menuconfig: scripts/config/mconf prepare-tmpinfo FORCE
 	[ -L .config ] && export KCONFIG_OVERWRITECONFIG=1; \
 		$< Config.in
 
+xconfig: scripts/config/qconf prepare-tmpinfo FORCE
+	if [ \! -e .config -a -e $(HOME)/.openwrt/defconfig ]; then \
+		cp $(HOME)/.openwrt/defconfig .config; \
+	fi
+	$< Config.in
+
 prepare_kernel_conf: .config FORCE
 
 ifeq ($(wildcard staging_dir/host/bin/quilt),)