Disable stripping pcc tool.

We don't have a tool that strips tools -- we have only a tool that
strips target programs.  $TOOLDIR/bin/$PLATFORM-install supports -s
by invoking the target-stripping tool, which chokes if you try to use
it to strip tools on a sufficiently different cross build.  So let's
just not strip the pcc tool -- it's tiny enough that I'm not worried
about its unstripped size!

(riastradh)