The former ldso-startup static library (now called ldso_so_support) is
used to spice each shared object/library with local support code for the
dynamic linker (execution of static constructors and ARM-EABI).
Therefore, the library must be statically linked to each dynamic
library.
As a result recipes for dynamic libraries must always depend on the "so"
API, which makes ldso_so_support.mk and so_support.c available
independent of "base". Additionally, ldso_so_support is also provided in
the libc API to cut the dependency early for libc/posix libraries.
Issue #3720
