Variable TARGET_TRIPLE is used as argument to clang's "-target" parameter specially when cross compiling.
It's expected to be in the form "<arch><sub>-<vendor>-<sys>-<abi>" (see https://clang.llvm.org/docs/CrossCompilation.html#target-triple), but it's currently calculated as "<arch><sub>-<abi>-<sys>"
*note <sub> is ignored in this patch as well