[lldb] Fix TestImportStdModule on some setups by testing minmax instead of abs

Some downstream forks of LLDB change parts of the test setup in a way that
causes lldb to somehow resolve `std::abs` (probably to `::abs`). This patch
changes the tested function here to be `std::minmax` which (hopefully) doesn't
have any identically named functions that LLDB could find and call. Just to be
extra safe this also explicitly specified the template arguments so that in
case there is a `minmax` non-template function we still don't end up calling it
from this test.