Reapply: Fix warning: comparison of integers of different signs

Buildbot failure:
https://lab.llvm.org/buildbot/#/builders/36/builds/26925

Review & commit:
https://reviews.llvm.org/D132224
https://reviews.llvm.org/rG171f7024cc82e8702abebdedb699d37b50574be7

llvm/unittests/IR/DebugInfoTest.cpp

@@ -506,7 +506,7 @@ TEST(AssignmentTrackingTest, Utils) {
   // 4. Check that deleting works and applies only to the target function.
   at::deleteAll(&Fun1);
   // There should now only be the alloca and ret in fun1.
-  EXPECT_EQ(Fun1.begin()->size(), 2);
+  EXPECT_EQ(Fun1.begin()->size(), 2u);
   // fun2's alloca should have the same DIAssignID and remain linked to its
   // llvm.dbg.assign.
   EXPECT_EQ(Fun2ID, cast_or_null<DIAssignID>(