[LLVMdev] cmake doesn't build libLTO with debug info

[Duncan P. N. Exon Smith]

cmake+ninja doesn’t build libLTO with debug info (at least, not on OS X
Mavericks).  I expect this applies to our cmake setup generally, although
I’ve only tested cmake+ninja.  A workaround is to manually run dsymutil
on libLTO.dylib before starting a debug session.

There appear to be a couple [1] of [2] open PRs about related problems
when building debug shared libraries with cmake.

Are there any cmake hackers around that know how to fix this?  Should I
file a separate PR?

[1]: http://llvm.org/bugs/show_bug.cgi?id=13465
[2]: http://llvm.org/bugs/show_bug.cgi?id=15242