[clang] Cleanup IncludeLocMap

CompilerInstance can re-use same SourceManager across multiple
frontendactions. During this process it calls
`SourceManager::clearIDTables` to reset any caches based on FileIDs.

It didn't reset IncludeLocMap, resulting in wrong include locations for
workflows that triggered multiple frontend-actions through same
CompilerInstance.

Author: kadircet

clang/lib/Basic/SourceManager.cpp

@@ -350,6 +350,7 @@ void SourceManager::clearIDTables() {
   LastLineNoContentCache = nullptr;
   LastFileIDLookup = FileID();
 
+  IncludedLocMap.clear();
   if (LineTable)
     LineTable->clear();