Currently, clang defines the three macros sparcv9, sparcv9__
and sparc_v9 when targeting the V8+ baseline, i.e. using the
V9 instruction set on a 32-bit target.
Since neither gcc nor SolarisStudio define sparcv9 and sparcv9__
when targeting V8+, some existing code such as the glibc breaks when
defining either of these two macros on a 32-bit target as they are
used to detect a 64-bit target. Update the tests accordingly.