Let CompilerInvocation initialization indicate failure

Let CompilerInvocation initialization indicate failure

This fixes the FIXMEs in ParseAnalyzeArgs. (Also a
precursor to moving the analyzer into an AST plugin.)

For consistency, do the same with AssemblerInvocation.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147218 91177308-0d34-0410-b5e6-96231b3b80d8