Add [install] section to fpm.toml

[moriglia]

This commit allows for installation of the stdlib, instructing fpm to install (if the prefix is not modified):

• libstdlib.a file --> ~/.local/lib/
• .[s]mod files --> ~/.local/include/

Example:
fpm install --compiler=gfortran-11 --profile release

Resolves #782

[perazz]

Thank you @moriglia, LGTM. Definitely a good idea, since this is a library. Let's wait for another review and comments.

[jvdp1]

Thank you @moriglia . It makes sense to me. It might be good to mention this new behaviour in the README.

[jvdp1]

cc: @jalvesz

[jalvesz]

LGTM @moriglia thanks for this contribution!

[moriglia]

Thank you all for your positive feedback!

It might be good to mention this new behaviour in the README.

Sure, I think I should open a separate PR though, since the README is present only on the master branch. Unless you want it to appear also on the stdlib-fpm branch. In which branch do you think the README edit would be more appropriate?

[jalvesz]

The stdlib-fpm branch is a subproduct of the automatic github CI. All contributions should be made through the master branch. You can add the info either around here https://github.com/fortran-lang/stdlib/blob/master/README.md#build-with-fortran-langfpm or here https://github.com/fortran-lang/stdlib/blob/master/README.md#using-stdlib-with-fpm. Also, all fpm actions are possible with the master branch following the fypp preprocessing as discribed in the first link. So if one uses the master branch, installation through fpm is possible.

[perazz]

@jalvesz is right, thank you for noticing it. These changes should be moved to the main branch fpm.toml

[moriglia]

The stdlib-fpm branch is a subproduct of the automatic github CI. All contributions should be made through the master branch. You can add the info either around here https://github.com/fortran-lang/stdlib/blob/master/README.md#build-with-fortran-langfpm or here https://github.com/fortran-lang/stdlib/blob/master/README.md#using-stdlib-with-fpm. Also, all fpm actions are possible with the master branch following the fypp preprocessing as discribed in the first link. So if one uses the master branch, installation through fpm is possible.

While reading the README to edit it, right before reading your message, I just realised that this PR is on the wrong branch.
I will revert to draft.