Choose default stdlib for clang

Hi,
How can I configure clang to use “-stdlib=libc++” by default instead of libstdc++?
If it’s not possible, can I compile my own version to do it?

I found a place suggested running this command to compile clang for this purpose:

…/llvm/configure CXXFLAGS="-stdlib=libc++ -std=c++11" OBJCXXFLAGS="-stdlib=libc++ -std=c++11" LDFLAGS="-stdlib=libc++"

But I see that the autoconf build system is deprecated.
Is there a cmake alternative for that command?

Or any other way to make clang use libc++ by default?

Thanks!

Oren