libc: Eliminate duplicate copies of __vdso_gettc.c

[kib]

I am fine with it.

Myself, I would use the name trivial_vdso_tc.c, but it is only a weak suggestion.

[emaste]

lib/libc/arm/sys/Makefile.inc

3

I went with trivial- for consistency with the getcontextx change, but I agree this is a bit awkward. I might use trivial-vdso_tc.c instead.

[emaste]

Closed by commit rS281004 (authored by @emaste).