Fix build-many-glibcs.py --strip for installed library renaming

The renaming of installed shared libraries to use the SONAME directly
rather than linking to a versioned name stopped build-many-glibcs.py
--strip (used to facilitate comparing binaries before and after
changes that aren't meant to change any generated code in installed
glibc shared libraries) from stripping most of the installed shared
libraries, because it stripped only the *.so names.  Fix it to strip
*.so* names instead and to detect the case of linker scripts using
grep instead of hardcoding particular files that are linker scripts.

Tested with build-many-glibcs.py --strip.