Changes

[InstCombine] keep assumption before sinking calls
Summary: in the following C code the branch is not removed by clang in
O3.
``` int f1(char* p) {
   int i1 = __builtin_strlen(p);
   if (!p)
       return -1;
   return i1;
}
``` The issue is that the call to strlen is sunk to the following block
by instcombine. In its new place the call to strlen doesn't dominate the
use in the icmp anymore so value tracking can't see that p cannot be
null. This patch resolves the issue by inserting an assumption at the
place of the call before sinking a call when that call can be used to
prove an argument to be nonnull. This resolves this issue at O3.
Reviewers: majnemer, xbolva00, fhahn, jdoerfert, spatel, efriedma
Reviewed By: jdoerfert
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69477

Always do a clean build on llvm-clang-x86_64-expensive-checks-win.

Force LIT verbose mode for some ARM builders to prevent a timeout on
clean builds.