[Windows] Partially revert r254363 until I can test the right fix.

Reported by:  David Blaikie

llvm-svn: 254378
diff --git a/llvm/lib/Support/Windows/DynamicLibrary.inc b/llvm/lib/Support/Windows/DynamicLibrary.inc
index e612283..17418b0 100644
--- a/llvm/lib/Support/Windows/DynamicLibrary.inc
+++ b/llvm/lib/Support/Windows/DynamicLibrary.inc
@@ -60,8 +60,12 @@
     if (OpenedHandles == 0)
       OpenedHandles = new DenseSet<HMODULE>();
 
-    if (!fEnumerateLoadedModules)
-      assert(loadDebugHelp() && "These APIs should always be available");
+    if (!fEnumerateLoadedModules) {
+      if (!loadDebugHelp()) {
+        assert(false && "These APIs should always be available");
+        return DynamicLibrary();
+      }
+    }
 
     fEnumerateLoadedModules(GetCurrentProcess(), ELM_Callback, 0);
     // Dummy library that represents "search all handles".