I have a fresh install of Xcode 12 + CLT on Big Sur (no universal). I am trying to install llvm and it claims it cannot find libc++ library. There is a soft link in the / usr/lib as expected but no target libc++.1.dylib When I compare to my "stable" Catalina (where I also install Xcode 12 + CLT) I can find the library however the time stamp is June 5th. I suspect it comes from Xcode 11.6 Beta +CLT. I am the feeling it is missing from Xcode 12 anyone has any idea? my thinking at the moment install 11.6 beta and move on to 12.

Hi there since I installed Xcode 13 b3, codes running under python 3.9.6 hang at various stages: I have no error messages just that python resources jump to >100% of CPU. This happens either loading a module (e.g. from astropy.modeling import models - but from astropy.constants.si import c its fine) or creating a reasonably sized array with numpy.arange(). I reinstalled Xcode 12.5.1 with its CLT and the code loads and creates what is needed. My vague idea is that the memory resources are badly handled using Xcode 13+CLTs (ahh everything worked fine with Xcode 13 b1) with Xcode 13 I have been using: Big Sur 11.5, or Monterey 12.0b3 . so the machine seems not to be an issue. any ideas?