Various fixes and additions to creduce-clang-crash.py
Various fixes and additions to creduce-clang-crash.py

Some more additions to the script - mainly reducing the clang args after
the creduce run by removing them one by one and seeing if the crash
reproduces. Other things:

- remove the --crash flag when "fatal error" occurs
- fixed to read stack trace functions from the top
- run creduce on a copy of the original file

Patch by Amy Huang!

Differential Revision: https://reviews.llvm.org/D59725


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@357290 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang