Update install.sh to actually install Caffeine

[bonachea]

./install.sh currently defaults to installing software as follows:

Build/install dependencies (those needed only to build/install Caffeine):

• GCC, Make, fpm, pkg-config, realpath
  • installed using HomeBrew to the default system HomeBrew install path (e.g. /usr/local)

Use dependencies (those also needed to use Caffeine post-install):

• GASNet-EX
  • Installed to install.sh --prefix, defaulting to ~/.local
• Caffeine
  • Currently not installed at all!

This issue requests installer updates to install the Caffeine libraries and any necessary headers to the user-provided install.sh --prefix location

[bonachea]

FWIW current fpm behavior:

$ ./build/run-fpm.sh install
<ERROR>Project does not contain any installable targets
STOP 1

We don't currently even write $PREFIX into fpm.toml, which is presumably one requirement to resolve this issue.

[ktras]

@everythingfunctional, as seen above, the fpm install command doesn't currently work, so perhaps you could help give clues as how to resolve this.