(FACT-1276) Make external facts dir absolute instead of canonicalizing

[branan]

It's not necessary to get the full canonical path for external facts
dir - we only need it to be absolute. Attempting to canonicalize paths
is more expensive, and can fail on Windows when boost::filesystem is
built to support Windows 2003, as we do.

[kylog]

when boost::filesystem is built to support Windows 2003, as we do

I thought we had dropped the 2003-supporting builds? I may have confused intention and reality (or branches). /cc @MikaelSmith

[branan]

In that case, another fix for this is to build boost::filesystem with -D_WIN32_WINNT=0x0600. It's not so much that we're explicitly building support for NT 5, so much as that we haven't opted in to breaking compatibility

[MikaelSmith]

Ah, possible but a little more involved. Is there value to canonicalizing the path?

[branan]

Regardless of the windows situation, though, canonicalization can be a very expensive operation (lots of stat calls) vs just creating an absolute path and letting the kernel do it's job to follow symlinks

[branan]

@MikaelSmith I don't think there's any value to canonicalizing in this case

[MikaelSmith]

I'll add a ticket for using _WIN32_WINNT=0x0600 for Windows builds; that's unrelated to this change then.