Always pass false for exe in elf_add call.

Always pass false for exe in elf_add call.

Basically, if you pass the isExe flag to elf_add, libbacktrace will
see that it's an ET_DYN executable which means that the sections
can be relocated on load so it will defer to dl_iterate_phdr to get
the real addresses. It will do that only when you call
backtrace_pcinfo which, behind the scenes, ends up calling
backtrace_initialize and that will do the dl_iterate_phdr for the
executable which is wrong since the executable we want to get the
symbols on is not the current one (which is heaptrack_interpret) and
we already get the base addresses correctly from the main process
through the pipe. So there's no need to ever pass isExe = true.