Link to AggressiveInstCombine in a few places. Unbreaks build for me.

/usr/local/bin/ld.lld: error: undefined symbol: llvm::createAggressiveInstCombinerPass()
>>> referenced by cc1_main.cpp
>>>               tools/clang/tools/driver/CMakeFiles/clang.dir/cc1_main.cpp.o:(_GLOBAL__sub_I_cc1_main.cpp)

And so on

The bot coverage is clearly missing.

llvm-svn: 330694