[AIX] Fixed a link error.

Summary:

 "Speculative fix for link failure on bots" with a mention of "the clang-ppc64le-rhel bot fails on link: http://lab.llvm.org:8011/#/builders/57/builds/2307/steps/6/logs/stdio".

PPCAsmPrinter.cpp:(.text._ZN12_GLOBAL__N_116PPCAIXAsmPrinter19emitFunctionBodyEndEv+0x2f8): undefined reference to `llvm::XCOFF::getNameForTracebackTableLanguageId(llvm::XCOFF::TracebackTable::LanguageID)'
PPCAsmPrinter.cpp:(.text._ZN12_GLOBAL__N_116PPCAIXAsmPrinter19emitFunctionBodyEndEv+0x2170): undefined reference to `llvm::XCOFF::parseParmsType(unsigned int, unsigned int)'