To make use of SPARC support in `getHostCPUName` as implemented by D130272
<https://reviews.llvm.org/D130272>, this patch uses it to handle
`-mcpu=native` and `-mtune=native`. To match GCC, this patch rejects
`-march` instead of silently treating it as a no-op.
Tested on `sparcv9-sun-solaris2.11` and checking that those options are
passed on as `-target-cpu` resp. `-tune-cpu` as expected.
Differential Revision: https://reviews.llvm.org/D130273
Rainer Orth