[KernelAddressSanitizer] Fix globals exclusion for indirect aliases

GlobalAlias::getAliasee() may not always point directly to a
GlobalVariable. In such cases, try to find the canonical GlobalVariable
that the alias refers to.

Link: https://github.com/ClangBuiltLinux/linux/issues/1208

Reviewed By: dvyukov, nickdesaulniers

Differential Revision: https://reviews.llvm.org/D92846

(cherry picked from commit c28b18af)