future pg+llvm compilation is broken

Hello devs,

  commit 2c24051bacd2d0eb7141fc4adb870281aec4e714
  Author: Craig Topper <craig.topper@gmail.com>
  Date:   Fri Apr 24 22:12:21 2020 -0700

     [CallSite removal] Rename CallSite.h to AbstractCallSite.h. NFC

     The CallSite and ImmutableCallSite were removed in a previous
     commit. So rename the file to match the remaining class and
     the name of the cpp that implements it.

Hence :

  .. llvmjit_inline.cpp
  llvmjit_inline.cpp:59:10: fatal error: llvm/IR/CallSite.h: No such file or
  directory
    59 | #include <llvm/IR/CallSite.h>
       |          ^~~~~~~~~~~~~~~~~~~~

Which is why animal seawasp is in now the red.

It looks unlikely that it will vanish, so pg must probably start aiming at 
the moving llvm target.

-- 
Fabien.