Makefile.am: Get rid of redundant linker arguments

I had previously added all static libraries twice to easily deal with ld's
dependenc on proper argument order.  This patch lists them in the right order,
eliminating the need for redundancy.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Replace built-in bash with bash builtin

It turns out bash has support for loading shared objects via the "enable -f"
command.  This means we can extend bash on any system without forking, while
also supporting nested invocations.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>