When libc++/libc++abi are built with exceptions disabled, the
new implementation there does not throw an exception for
an error, but it also does nothing else. So new ends up returning
a zero if malloc did, which can break programs.

Technically libc++/libc++abi are doing a reasonable thing here,
just removing all exceptions-related code when exceptions are
disabled. The assumption is likely that a user program would
set a new_handler if an error is desired. For us, we have to change
this as our default mode is to have exceptions disabled, and we
don't want users to need to know they need to do anything.

This makes it abort instead. (Note that without growth this
happened to always work, since we abort on any failing allocation.
With growth enabled, though, malloc returns 0, and we end up
in this situation.)

Fixes #11042 As discussed there I also looked at the option of
installing a set_new_handler that does an abort. That ends up
increasing code size by a little (bit less than 1%) because if adds
a global constructor, a function to the table, and some memory
operations. It seems better to just modify new itself which avoids
all that.