Summary:
Change how the output directory is specified when invoking
opt-viewer.py, from `opt-viewer.py yaml_file_one yaml_file_two output_dir` to
`opt-viewer.py -o output_dir yaml_file_one yaml_file_two`.
This makes it easier to pipe the results of another command into
opt-viewer.py. For example:
```
find . -name "*.yaml" -print | xargs /path/to/opt-viewer.py -o html
```
Reviewers: anemet, davidxl
Reviewed By: anemet
Subscribers: fhahn, llvm-commits
Differential Revision: https://reviews.llvm.org/D34711
llvm-svn: 306694
39b88f01a5