Debugger: Use LD_PRELOAD to load debugging helper.
on UNIX. Either set the LD_PRELOAD environment variable using a gdb command or have the TermGdbAdapter set the variable for the debuggee. For the remote adapter, switch on toolchain. dlopen() is a fallback for platforms where it is not supported and attaching to running processes. Fixes a crash with gdb 7.0 (and spurious gdb 6.8 crashes with dlopen()). Reviewed-by: hjk <email@example.com>