Summary:
Currently the llvm-xray commandline tool fails to handle the case for
when no subcommand is provided in a graceful manner. This fixes that to
print the help message explaining the subcommands and the available
options.
Reviewers: pcc, pelikan
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D31409
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298975 91177308-0d34-0410-b5e6-96231b3b80d8