[LLD] Silence warning when compiling with MSVC targetting x86

This fixes:
```
[5383/6995] Building CXX object tools\lld\COFF\CMakeFiles\lldCOFF.dir\PDB.cpp.obj
C:\git\llvm-project\lld\COFF\PDB.cpp(835): warning C4018: '>=': signed/unsigned mismatch
```
GitOrigin-RevId: 3fec25c55f1890c138e64548dc074b4593e0a26c
diff --git a/COFF/PDB.cpp b/COFF/PDB.cpp
index 8b81a71..35e4c68 100644
--- a/COFF/PDB.cpp
+++ b/COFF/PDB.cpp
@@ -832,7 +832,7 @@
   assert(vaBegin > 0);
   auto relocs = sc->getRelocs();
   for (; nextRelocIndex < relocs.size(); ++nextRelocIndex) {
-    if (relocs[nextRelocIndex].VirtualAddress >= vaBegin)
+    if (relocs[nextRelocIndex].VirtualAddress >= (uint32_t)vaBegin)
       break;
   }
 }