r266298: make buildworld fail: fatal error: 'llvm/ADT/APFloat.h' file not found #include "llvm/ADT/APFloat.h"

With 11.0-CURRENT's sources (r266298) buildworld fails:

[...]
/usr/src/lib/clang/libllvmsupport/../../../contrib/llvm/lib/Support/APFloat.cpp:15:10:
fatal error: 'llvm/ADT/APFloat.h' file not found #include "llvm/ADT/APFloat.h"
         ^
1 error generated.
/usr/src/lib/clang/libllvmsupport/../../../contrib/llvm/lib/Support/APInt.cpp:16:10:
fatal error: 'llvm/ADT/APInt.h' file not found #include "llvm/ADT/APInt.h"

oh