[PATCH] build: create $(PKG_SYMVERS_DIR) if non-existent

[Hannu Nyman]

Paul Spooren wrote at Tue Nov 17 16:53:29 EST 2020:
 > Could you please provide an example when that fails? E.g. what package
 > makes the SDK copy things there?

Pretty much all kernel related packages, like I already disgnosed a few days 
ago in
http://lists.openwrt.org/pipermail/openwrt-devel/2020-November/032115.html

Examples that I used then were cryptodev-linux and exfat.

Buildbot has been broken regarding the kernel packages for the last 3-4 days.

Kernel packages failing cause then carnage with other packages

https://downloads.openwrt.org/snapshots/faillogs/x86_64/base/
https://downloads.openwrt.org/snapshots/faillogs/x86_64/packages/