[dsymutil] Use option categories.

Prevent all the unrelated LLVM options to appear in the -help output
by introducing a tool specific option category. As a drive-by improve
the wording of the help message.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243583 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed