Normally, we'd split the string at the last dash. However if the
tool name is "llvm-<tool>", make sure to include "llvm-" in the
tool name part when splitting the executable name.
In llvm-wrapper, don't add a duplicate "llvm-" prefix for the tool
name in these cases.
This saves a lot of diskspace, when symlinks are turned into full
copies of the tools on windows, as the symlinks only point to a small
wrapper instead of to the full tool.
Martin Storsjö