[llvm] [llvm-gsymutil] Print a DWO file missing warning under --quiet flag (PR #68062)

[Alexander Yermolovich via llvm-commits]

ayermolo wrote:

Right now behavior is different based on whether it's --quite or not.
Maybe it's better to change it based on verbosity?
On minimum verbosity it will print once that dwo was not found either to logging or errs(), for some higher verbosity it will print all.
For only once case, would be useful to know how many were missed?

https://github.com/llvm/llvm-project/pull/68062