Enable top-level parallel build and reproducible builds

Because systemd-networkd's resolver configuration is broken by the
parallel build (see the bugreport), hack this around by a manual overlay
configuration.

Change-Id: I801e9d9c35511041ca61df6876305a26a6cc14ed
Bug: https://patchwork.ozlabs.org/patch/1019149/#2064351
diff --git a/configs/czechlight_clearfog_defconfig b/configs/czechlight_clearfog_defconfig
index f20c5eb..f6be72a 100644
--- a/configs/czechlight_clearfog_defconfig
+++ b/configs/czechlight_clearfog_defconfig
@@ -6,6 +6,8 @@
 BR2_ENABLE_DEBUG=y
 BR2_STRIP_EXCLUDE_FILES="cla-* netopeer2* sysrepo* libsysrepo* libSysrepo* libnetconf2* libyang*"
 BR2_STRIP_EXCLUDE_DIRS="/usr/lib/libyang /usr/lib/sysrepo"
+BR2_REPRODUCIBLE=y
+BR2_PER_PACKAGE_DIRECTORIES=y
 BR2_SSP_STRONG=y
 BR2_TOOLCHAIN_EXTERNAL=y
 BR2_TOOLCHAIN_EXTERNAL_GDB_SERVER_COPY=y