Resolve ambiguity between llvm::make_unique and std::make_unique.

Intorduced in r219098.
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219105 91177308-0d34-0410-b5e6-96231b3b80d8
Add subtarget caches to aarch64, arm, ppc, and x86.
These will make it easier to test further changes to the
code generation and optimization pipelines as those are
moved to subtargets initialized with target feature and
target cpu.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219106 91177308-0d34-0410-b5e6-96231b3b80d8