Test suite support for setting arguments through the environment

Set your env variable LLDB_TEST_ARGUMENTS to one or more options to be passed to the lldb test suite and those will be picked automatically

No more fighting about whether the progress bar is good or bad :-)



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@184615 91177308-0d34-0410-b5e6-96231b3b80d8