Adding test to cover the correct import of SourceLocation pertaining to a built-in during expression parsing
Summary: This tests a fix in the ASTImpoter.cpp to ensure that we import built-in correctly,
see differential: https://reviews.llvm.org/D58743
Once this change is merged this test should pass and should catch regressions in this feature.
Differential Revision: https://reviews.llvm.org/D58790