Start building libnetconf2-cpp

It is not used anywhere yet, but it's available to the CI, and it's
getting built.

Change-Id: I6c718b0ec5931bac5668ebc1abbea45fe27898d0
Depends-on: https://gerrit.cesnet.cz/c/CzechLight/dependencies/+/5432
diff --git a/configs/czechlight_clearfog_defconfig b/configs/czechlight_clearfog_defconfig
index 152f0b6..bf1abe4 100644
--- a/configs/czechlight_clearfog_defconfig
+++ b/configs/czechlight_clearfog_defconfig
@@ -51,6 +51,7 @@
 BR2_PACKAGE_UBOOT_TOOLS_KWBOOT=y
 BR2_PACKAGE_CA_CERTIFICATES=y
 BR2_PACKAGE_LIBGPIOD_TOOLS=y
+BR2_PACKAGE_LIBNETCONF2_CPP=y
 BR2_PACKAGE_NETOPEER2=y
 BR2_PACKAGE_NETOPEER2_CLI=y
 BR2_PACKAGE_ELFUTILS=y