Provide a class to generate a SHA1 from a sequence of bytes, and
a convenience raw_ostream adaptor.
This will be used to provide a "build-id" by hashing the Module
block when writing bitcode. ThinLTO will use this information for
incremental build.
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265094 91177308-0d34-0410-b5e6-96231b3b80d8