This fixes a syntax error in the extra_configure_args provided to
getClangWithLTOBuildFactory, we shouldn't be surrounding the options
with double quotes.
Once that is fixed, I realized from testing the failing command locally
that it will still fail, because the clang-specific extra_configure_args
are also used by the initial stage1 build with the system compiler,
which is gcc. We only want these for the last stage, where LTO is
performed. Added a new parameter to getClangWithLTOBuildFactory,
extra_configure_args_lto_stage, to pass the options only to that LTO
Is there a way to test my change to ClangLTOBuilder.py?