[dsymutil] Add missing raw_svector_stream::resync() calls.

Also, after looking at the raw_svector_stream internals, increase the
size of the SmallString used with it to prevent heap allocation.

Issue found by the Asan bot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232335 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed