flux plugin build and install broken

[grondo]

It appears that in c3ef9a2 some of the autotools setup for the Spindle Flux plugin was removed.

Unfortunately, this breaks proper (or perhaps more correctly _convenient) installation of the Flux plugin. Things that would help the install of the flux plugin include:

• It is customary for plugins to not have a lib prefix, e.g. the Flux plugin should be spindle.so. This matches how Flux expects plugins to be named, but isn't critical if there is a reason Spindle wants the lib prefix.
• The plugin should be installed by default to the Flux shell pluginpath (this was previously captured and defined in configure.ac). For a spack package or side install, a flux shell spindle.lua rc file should be installed and added to FLUX_SHELL_RC_PATH.

I'm also not seeing any checks for libflux-core.so and libflux-hostlist.so, but I must be missing this because the flux plugin is built with these libs and FLUX_CORE_LIBS and FLUX_CORE_CFLAGS etc are defined in the Makefiles, so I apologize if I missed something obvious.

[mplegendre]

I'm cautious about going to spindle.so for the flux plugin. Spindle already has a libspindle.so for its user interface library, and mixing those names could be confusing. Could we symlink a spindle.so in the flux plugin space to a libspindleflux.so in the spindle space?

Will investigate the pluginpath issue.

[grondo]

Eh, like I said the naming isn't critical, by default the Flux job shell will load *.so from the plugin search path, so either fluxspindle.so or libfluxspindle.so would work.