Add CMAKE option to control building/installing static libraries

[timsnyder]

Currently, XRT has several libraries that it builds both shared and static and it seems in general to always explicitly specify either SHARED or STATIC when calling add_library() in cmake files.

For building XRT as a conda package, the community generally avoids providing static libraries for the reasons outlined in https://github.com/conda-forge/cfep/blob/main/cfep-18.md.

Please add a cmake option that can be used to disable installing static libraries. If XRT only cares to deliver STATIC or SHARED, you could switch to using the standard BUILD_SHARED_LIBS cmake flag. But, if you want to keep delivering both, you will need to create your own XRT_INSTALL_STATIC_LIBS option.