Commit 69be352a19 restricted the MachO debugger support testcase to run on
Darwin only, but we still need to disable debugger support by default for
other noexec tests.
This patch introduces a -debugger-support option to llvm-jitlink that is
on-by-default when executing code, and off-by-default for noexec tests. This
should prevent regression tests from trying (and failing) to set up MachO
debugging support when running on non-Darwin platforms.
to explicitly enable/disable support.