Summary:
Most clang tools should ignore the -M
family of options because one wouldn't want them
to generate a new dependency (.d) file. However,
some tools may want this dependency file. This
patch creates a mechanism for them to do this.

This implementation just plumbs a boolean down
several layers of calls. Each of the modified calls
has several call sites, and so a single member
variable or new API entry point won't work.

An alternative would be to write a function to filter
the -M family of arguments out of CC1Args, and have
each caller call that function by hand before calling
newInvocation, Invocation::run, or buildAstFromCodeWithArgs.
This is a more complicated and error-prone solution.
Why burden all the callers to remember to use
this function?

But I could rewrite this patch to use that method if
that is deemed more appropriate.

Reviewers: klimek

Reviewed By: klimek

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D34304

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@307315 91177308-0d34-0410-b5e6-96231b3b80d8