[LNT] In command-line tool expand tilde when resolving commands.

[vsapsai]

Summary

The use case it addresses is being able to provide extra tools like

--use-lit=~/llvm/build/bin/llvm-lit

Currently lnt fails even if the file is present and executable. Error looks like

lnt error: LIT tool not found (looked for ~/llvm/build/bin/llvm-lit)

[vsapsai]

Thanks for review, Chris.

lnt/testing/util/commands.py

def which(command, paths=None):
     return None
 
 
 def resolve_command_path(name):
     """Try to make the name/path given into an absolute path to an
     executable.
 
     """
+    name = os.path.expanduser(name)
+
     # If the given name exists (or is a path), make it absolute.
     if os.path.exists(name):
         return os.path.abspath(name)
 
     # Otherwise we most likely have a command name, try to look it up.
     path = which(name)
     if path is not None:
         logger.info("resolved command %r to path %r" % (name, path))