Make loop counter unsigned in SymbolFilePDB::GetCompileUnitIndex

Summary: This fixes a clang warning.

Reviewers: zturner

Reviewed By: zturner

Subscribers: zturner, lldb-commits

Differential Revision: https://reviews.llvm.org/D42345

llvm-svn: 323075
diff --git a/lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp b/lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp
index 24e7e62..d008292 100644
--- a/lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp
+++ b/lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp
@@ -211,7 +211,7 @@
   if (!results_up)
     return;
   auto uid = pdb_compiland->getSymIndexId();
-  for (int cu_idx = 0; cu_idx < GetNumCompileUnits(); ++cu_idx) {
+  for (uint32_t cu_idx = 0; cu_idx < GetNumCompileUnits(); ++cu_idx) {
     auto compiland_up = results_up->getChildAtIndex(cu_idx);
     if (!compiland_up)
       continue;