Skip TestWatchedVarHitWhenInScope.py everywhere

The expression-hits tracking logic is not available on any platform. The
reason this tests happens to pass on some platforms is that the test is
written poorly -- it relies on the fact that post-main cleanup code will
write to the stack memory once occupied by the watched variable, but
this is not the case everywhere (e.g. linux glibc does not seem to do
this, but android's bionic library does).

llvm-svn: 327483