Intermittent kuksa.val build failures

kuksa.val seems to be regularly failing to build when testing the kirkstone 4.0.7 upgrade on the needlefish branch (see discussion in https://gerrit.automotivelinux.org/gerrit/c/AGL/AGL-repo/+/28482).  From inspection, it looks like the creation of the buildinfo.h header file is inherently racy with building the contents of kuksa-val-server/src, which we can hopefully fix with a patch.  It's not clear why we're just seeing this now when building the kirkstone upgrade for just needlefish branch, possibly the timing ends up just right to miss the race somehow.