[dsymutil] Avoid calling getStringTableData() for each symbol. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224360 91177308-0d34-0410-b5e6-96231b3b80d8
[dsymutil] Pass the verbosity flag down to the processing. NFC for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224361 91177308-0d34-0410-b5e6-96231b3b80d8