Clang17.0 can not find headers after building from source and installing it on macOS 10.15

I am on macOS 10.15
I compiled clang using Apple-Clang 12
I enabled the Release BUILD, and I selected projects “clang; lldb; lld”
I also changed via ccmake the configuration to build lldb framework and turned off the Tests.
Finally I changed the CMAKE_INSTALL_PREFIX because I did not want to override the apple-clang installation.

and then run cmake --build build --target install
followed by (6 hours later)
cd build && ninja install.

however, clang did not install the headers, when trying to include anything from the standard library headers, it can not find them, further more I checked that the directory:

bin/clang++…/include/c++/v1 does not exist.
It was not installed,
any ideas on what might caused clang installation to miss the headers?

here is an example of the output

You did not add libcxx to the enabled project. Thus it was not built.
See bootstrapping:

Will give it a try now, thanks!

This worked for the header problem, I encountered another one, which it was complaining about non-standard headers, like pthreads and the like.

I installed Xcode command line tools, and I exported the SDKROOT env variable to be
the same as:
xcrun --show-sdk-path --sdk macosx

not sure if that was the correct way, but it did solve it for now.