[llvm] [polly] [cmake] Don't install static extensions when linked into libLLVM (PR #88660)

[via llvm-commits]

xarblu wrote:

Nevermind, this still doesn't work the way I expected. While it does allow clang to fully dynamically link to a polly-enabled libLLVM clang will then hard-depend on polly symbols in libLLVM and break when libLLVM is build with polly disabled. 

https://github.com/llvm/llvm-project/pull/88660