kbuild: Use KCONFIG_CONFIG in buildtar

Previously, .config was used in buildtar script regardless of the value of
KCONFIG_CONFIG.
Signed-off-by: Nicolas Porcel <nicolasporcel06@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/package/buildtar

@@ -56,7 +56,7 @@ mkdir -p -- "${tmpdir}/boot"
 #
 # Try to install modules
 #
-if grep -q '^CONFIG_MODULES=y' "${objtree}/.config"; then
+if grep -q '^CONFIG_MODULES=y' "${KCONFIG_CONFIG}"; then
 	make ARCH="${ARCH}" O="${objtree}" KBUILD_SRC= INSTALL_MOD_PATH="${tmpdir}" modules_install
 fi
 
@@ -65,7 +65,7 @@ fi
 # Install basic kernel files
 #
 cp -v -- "${objtree}/System.map" "${tmpdir}/boot/System.map-${KERNELRELEASE}"
-cp -v -- "${objtree}/.config" "${tmpdir}/boot/config-${KERNELRELEASE}"
+cp -v -- "${KCONFIG_CONFIG}" "${tmpdir}/boot/config-${KERNELRELEASE}"
 cp -v -- "${objtree}/vmlinux" "${tmpdir}/boot/vmlinux-${KERNELRELEASE}"