Re-reland "[Option] Fix PR37006 prefix choice in findNearest"

This was first reviewed in https://reviews.llvm.org/D46776 and
landed in r332299, but got reverted because it broke the PS4
bots.

https://reviews.llvm.org/D50410 fixed this, and then this
change was re-reviewed at https://reviews.llvm.org/D50515 and
relanded in r341329. It got reverted due to causing MSan issues.
However, nobody wrote down the error message and the bot link
is dead, so I'm relanding this to capture the MSan error.
I'll then either fix it, or copy it somewhere and revert if
fixing looks difficult.

llvm-svn: 359580