clang.bbclass: Export YOCTO_ALTERNATE_LIBDIR and YOCTO_ALTERNATE_EXE_PATH
clang.bbclass: Export YOCTO_ALTERNATE_LIBDIR and YOCTO_ALTERNATE_EXE_PATH

These variables are used during target package compiles in packages
which user llvm-config e.g. libclc

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

kraj/meta-clang,kraj/meta-clang,kraj/meta-clang