[musl] Remove effective euid/egid based notion of libc.secure

This is not a useful notion for us. We don't have these IDs, for one
thing. Any per-process granting or denial of privilege is likely to
happen at another layer.

Change-Id: Ic4c5252af49013157c1adaab334ec96fb0e8e755

[ulib] [musl] Stub out getauxval

This API exists to query the auxv, which we do not have at all.
Handle a couple of known uses, and punt the general case.

Change-Id: Ie21dfea59f67eab7e42b0de8bdfec323af8a2276

[musl] clang format musl

Change-Id: I3bc6ab7655410514691cd07f08454f3afd41d9b3

[magenta] Initial commit