Convert the Archive API to use ErrorOr.

Now that we have c++11, even things like ErrorOr<std::unique_ptr<...>> are
easy to use.

No intended functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211033 91177308-0d34-0410-b5e6-96231b3b80d8
Fix pr17056.

This makes llvm-nm ignore members that are not sufficiently aligned for
lib/Object to handle.

These archives are invalid. GNU AR is able to handle this, but in general
just warns about broken archive members.

We should probably start warning too, but for now just make sure llvm-nm
exits with an 0.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211036 91177308-0d34-0410-b5e6-96231b3b80d8
Refactor the disabling of Thumb-1 LDM/STM generation

Originally I switched the LD/ST optimizer off in TargetMachine as it was previously, but Eric has suggested he'd prefer that it be short-circuited in the pass itself.

No functionality change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211037 91177308-0d34-0410-b5e6-96231b3b80d8