math/libdivsufsort: build and install the 64-bit library

[ngie]

Summary

This is needed for some downstream components like [1].

Signed-off-by: Enji Cooper <[e-mail]>

[1]: https://github.com/usnistgov/SP800-90B_EntropyAssessment

[ngie]

Install the 64-bit library pkg-config file as well

This allows programs which consume the pkg-config metadata to find/leverage the upstream
maintainer provided metadata to determine where/how to build dependent components.