Revert "Add disk_space() to llvm::fs"

Breaks windows bot.
This reverts commit r265050.
This reverts commit r265055.

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265062 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed