Retry: [profiling] Fix profile counter increment when emitting selects (PR32019)

Retry: [profiling] Fix profile counter increment when emitting selects (PR32019)

2nd attempt: the first was in r296231, but it had a use after lifetime
bug.

Clang has logic to lower certain conditional expressions directly into llvm
select instructions. However, it does not emit the correct profile counter
increment as it does this: it emits an unconditional increment of the counter
for the 'then branch', even if the value selected is from the 'else branch'
(this is PR32019).

That means, given the following snippet, we would report that "0" is selected
twice, and that "1" is never selected:

  int f1(int x) {
    return x ? 0 : 1;
               ^2  ^0
  }

  f1(0);
  f1(1);

Fix the problem by using the instrprof_increment_step intrinsic to do the
proper increment.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@296245 91177308-0d34-0410-b5e6-96231b3b80d8