[lldb][test_suite] skip tests of libstdcpp on Android and clean up
Summary: Delete the android target from libstdcpp test category, since android no longer support libstdcxx
Reviewers: xiaobai, labath
Reviewed By: labath
Subscribers: srhines, lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D64771
llvm-svn: 366770