/var/tmp/portage/sys-devel/clang-9999/work/clang-9999-abi_x86_32.x86/./bin/clang: symbol lookup error: /usr/lib32/libclangCodeGen.so.40: undefined symbol: _ZN4llvm9DIBuilder15createBasicTypeENS_9StringRefEyjj etc. Looks like we're missing LD_LIBRARY_PATH or rpath. The latter preferred.
This is fixed for some time already.