tvv authored Dec 02, 2015 and Ben Gamari committed Dec 02, 2015

This patch creates empty dump file when GHC was run with
`-ddump-rule-firings` (or `-ddump-rule-rewrites`) and `-ddump-to-file`
specified, and there were no rules applied. If dump already exists it
will be overwritten by empty one.

Test Plan: ./validate

Reviewers: austin, thomie, bgamari

Reviewed By: thomie, bgamari

Subscribers: thomie

Projects: #ghc

Differential Revision: https://phabricator.haskell.org/D1514

GHC Trac Issues: #10320