[compiler-rt] Fix broken SymInitialize unittest

Summary:
By adding the initialisation of the symbolisation library (DbgHelp)
we are swapping the order in which both warnings are produced.

We can't use CHECK-NEXT as the dbghelp warning is multiline.

Reviewers: rnk

Subscribers: kubabrecka, llvm-commits, wang0109, chrisha

Differential Revision: https://reviews.llvm.org/D22586

llvm-svn: 276228