run-tests.py: pass --install-scripts to setup.py
This avoids possible problems when the user has a ~/.pydistutils.cfg.
Fixes
issue638. Patch provided by Ralf Schmitt.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://www.selenic.com/mercurial/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.