All errors shown in the build log are related to the copy of llvm that comes with ClamAV, e.g.:

[  108s] In file included from ./llvm/include/llvm/Support/Allocator.h:17:0,
[  108s]                  from ./llvm/include/llvm/ADT/StringMap.h:18,
[  108s]                  from ./llvm/include/llvm/System/Host.h:17,
[  108s]                  from detect.cpp:29:
[  108s] ./llvm/include/llvm/Support/AlignOf.h:57:24: error: expected unqualified-id before 'alignof'
[  108s]  static inline unsigned alignof() { return AlignOf<T>::Alignment; }
[  108s]                         ^~~~~~~

Fixed in sr#402898.

Thanks.