clang: Use LLVM_USE_SPLIT_DWARF=ON
clang: Use LLVM_USE_SPLIT_DWARF=ON

This helps in consuming less memory during link stage and also fixed
link failures on mips64

Using clang cross itself ends up crashing
| clang-9: error: unable to execute command: Killed
| clang-9: error: linker command failed due to signal (use -v to see invocation)

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

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