[core] Lock interpreter in TCling::GetClassSharedLibs

Co-authored-by: Jonas Hahnfeld <[email protected]>

core/metacling/src/TCling.cxx

@@ -7025,6 +7025,11 @@ static std::string GetClassSharedLibsForModule(const char *cls, cling::LookupHel
 const char* TCling::GetClassSharedLibs(const char* cls)
 {
    if (fCxxModulesEnabled) {
+      // Lock the interpreter mutex before interacting with cling.
+      // TODO: Can we move this further deep? In principle the lock should be in
+      // GetClassSharedLibsForModule, but it might be needed also for
+      // getLookupHelper?
+      R__LOCKGUARD(gInterpreterMutex);
       llvm::StringRef className = cls;
       // If we get a class name containing lambda, we cannot parse it and we
       // can exit early.