Created attachment 145072 [details]
log of build failure
llvm-project trunk rev fcd549a7d8 from august 04 2019
https://cgit.freedesktop.org/mesa/mesa/commit/src/gallium/state_trackers/clover/llvm?id=6b8269d0bbded7a42cd2de2b50d077cf12157d15 seems a liklely cause.
Maybe the implementation in there is incomplete ?
Full build log attached.
You need clang SVN r367864 or newer. clang doesn't provide any way for clover to continue building against older SVN trunk snapshots.