installworld: improve portability of ldd use

[brooks]

Summary

b3b462229f97 added a case statement to ignore lines containing strings
in square brackets such as "[vdso]" and "[preloaded]". On MacOS
Monterey where /bin/sh may be zsh, this fails with:

/bin/sh: -c: line 0: syntax error near unexpected token `;;'

Invoke grep in the pipeline to remove such lines instead.

[brooks]

I've not tested this on a system that manifests the original issue due to lack of easy access last Friday, but it's straightforward, fixes build for me on MacOS, and works on example input.

[emaste]

OK