Since NetBSD 6, the base system has included clang.
It works on ARM, PowerPC, x86, and possibly SPARC64, but is not built by default.
To use it, set in mk.conf:

MKGCC=no
MKLLVM=yes
HAVE_LLVM=yes
PKGSRC_COMPILER=clang
CLANGBASE=/usr

And run "build.sh release". This will apply for both pkgsrc and base.

tunable	explanation
MKGCC=no	needed as building GCC alongside is not maintained
MKLLVM=yes	builds LLVM libraries
HAVE_LLVM=yes	controls clang being built
PKGSRC_COMPILER=clang	instructs pkgsrc it's clang
CLANGBASE=/usr	instructs pkgsrc where to look for the compiler

status

NetBSD-current clang build status