[cfe-dev] --split-dwarf silently fails on non-Linux platforms

[Ed Maste]

In r175814 -gsplit-dwarf was made into a no-op on non-Linux platforms,
but there's no explanation in the comment explaining what lead to the
change. -gsplit-dwarf requires a newer binutils, but that is also true
on Linux.

I'm looking into this for FreeBSD, and wonder if I should change the
three or so isOSLinux() conditions for split-dwarf to (isOSLinux() ||
isOSFreeBSD()), just remove them, or something else. I'm not fully
aware of the situation on Windows or Darwin, but it seems we could
handle it the same way on all ELF targets, at least.