Should we ship NDEBUG (no asserts) versions of system libraries

Our use of NDEBUG to disable asserts in system libraries is inconsistent today:

libcxx: Always define NDEBUG
libunwind: Always define NDEBUG
libmalloc: Defines `-debug` variant which doesn't define NDEBUG
libstubs: Defines `-debug` variant which doesn't define NDEBUG
libstandalonewasm: Always define NDEBUG

All other libraries do not define NDEBUG which means they include assertions. This includes libc, compiler-rt and libwasmfs.

For most of libc its not a huge deal since musl doesn't do at lot of asserting, but where have modified musl (for example in the pthread code we do have a bunch of asserts).

I guess we should probably define `-debug` versions of all libraries and link them when `ASSERTIONS` is enabled?