ctor/dtor nptl: Fix init and fini function compilation

ctor/dtor nptl: Fix init and fini function compilation

We need to define the rules for .S files so it
gets the include paths some architectures like mips
include headers

Some architectures e.g. SH have their own version
of pt-initfini.c so look for that first before resorting
to generic version of pt-initfini.c

Signed-off-by: Khem Raj <raj.khem@gmail.com>