Fix a nasty bug that Nate ran into. In particular, instead of emitting a 2+MB

Fix a nasty bug that Nate ran into.  In particular, instead of emitting a 2+MB
error message, print out:

llvm-link: error linking in 'g.2.rbc': Global Variable Collision on
' %struct.D_Reduction* %d_reduction_10_gram' - External linkage globals have
different initializers

That's a bit more concise, huh?

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15958 91177308-0d34-0410-b5e6-96231b3b80d8