Omit all the extra static attributes on subprograms in -gmlt

This omission will be done in a fancier manner once we're dealing with
"put gmlt in the skeleton CUs under fission" - it'll have to be
conditional on the kind of CU we're emitting into (skeleton or gmlt).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218098 91177308-0d34-0410-b5e6-96231b3b80d8
Describe the -gmlt optimization committed in the previous revision.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218099 91177308-0d34-0410-b5e6-96231b3b80d8