rapids_cpm_gtest(BUILD_STATIC) now doesn't search for a local version

[robertmaynard]

Description

This is important so that we don't pick up static system installs of GTest which don't have PIC enabled.

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.
• [x] The cmake-format.json is up to date with these changes.

[vyasr]

/merge

[vyasr]

Verified that this fixes the issue. This run in rmm succeeded, while the prior run (before this PR) failed