[clang] [clang][analyzer] Fixed test 'ctu-import-type-decl-definition' and ASTImporter (PR #158016)

[Balázs Kéri via cfe-commits]

balazske wrote:

Arguments to `clang_extdef_map` were wrong in the test, so the mapping file was empty and no AST import happened. If the test is correct, the fault is fixed only the type definition is always imported (no use of `isUsed`).

https://github.com/llvm/llvm-project/pull/158016