Fix swig scripts install target name

LLVM install component targets needs to be in the form of: install-{target}[-stripped]

I tested with:
```
cmake ... -DLLVM_ENABLE_PROJECTS="clang;lldb" -DLLVM_DISTRIBUTION_COMPONENTS="lldb;liblldb;lldb-python-scripts;" ...
DESTDIR=... ninja install-distribution
```

@JDevlieghere `finish_swig_python_scripts` is a really weird name for a distribution component, any reason that it has to be this way?

Differential Revision: https://reviews.llvm.org/D86235