Remove PDBFileBuilder::build() and related functions.

PDBFileBuilder supports two different ways to create files.
One is PDBFileBuilder::commit. That function takes a filename
and write a result to the file. The other is PDBFileBuilder::build.
That returns a new PDBFile object.

This patch removes the latter because no one is using it and
in a real life situation we are very unlikely to need it.
Even if you need it, it'd be easy to write a new PDB to a memory
buffer and read it back.

Removing PDBFileBuilder::build enables us to remove other classes
build transitively.

Differential Revision: https://reviews.llvm.org/D26987

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287697 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed