Fix LIT test failure encountered on AIX

```
fatal error: error in backend: getLangStandardForKind() on unspecified kind
```

Clang :: Modules/preprocess-module.cpp
Clang :: Modules/no-module-map.cpp
Clang :: Modules/preprocess-build-diamond.m
Clang :: Modules/preprocess-decluse.cpp
Clang :: Modules/string_names.cpp

Fix to prior commit f38eff77, D103707