[Support][CachePruning] Fix regression in pruning interval
[Support][CachePruning] Fix regression in pruning interval

Fixed broken comparison.
borked by: rL284966 (see: https://reviews.llvm.org/D25730).

Differential Revision: https://reviews.llvm.org/D40119

This is a second attempt to commit this.
The first attempt broke lld and gold tests that had been written against
the incorrect behaivour.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@318524 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm