Rework the creation of build.sh so it's not a template.

Rework the creation of build.sh so it's not a template.

* build.sh: Rename from build.template.  Get the list of objects
from the Makefile.  Move configure-replaced variables ...
* build.cfg.in: to this new .in file.
* configure.ac: Remove special handling of build.sh.in and add
build.cfg as a generated file.
* Makefile.am (EXTRA_DIST): Remove build.sh.in and add build.sh
and build.cfg.in for build.sh.in.
* maintMakefile: Remove handling for build.template.  Treat
build.sh as a source file, not a generated file.
* .gitignore: Ignore generated build.cfg file.