Add CMake components to neatly install individual libraries

[delta512]

Dear maintainers,
as you might guess from the title, I've just specified the COMPONENT attribute for each install() directive.
These are qrcodegen for the C library and qrcodegencpp for the C++ implementation.

This enables installing only one of the two library flavors with commands in the form:
cmake --install <build_dir> [--prefix <install_dir>] --component <component>

My use case for this is to produce split packages in a more elegant way. As an example, split packages for Arch Linux can be created with both libraries sharing a common build and test process, then they can be packaged separately without all those clean-up instructions (as seen in the qrcodegen-cmake AUR package).

Thanks for your time, hope you'll find it useful as well.

Cheers!

[leha-bot]

Big thanks for your PR! Looks great for me
One negligible comment: may you update the README for users how to install both libraries with CMake components (like "sudo cmake --install qrcodegen-build --component qrcodegencpp")

[xvitaly]

Please squash your commits to a single one and add a sign-off (you can use git commit -s and the Git will handle it automatically).

We need signed-off commits for sending changes to the upstream.

[delta512]

Hi all, glad you appreciated it.

Please squash your commits to a single one and add a sign-off (you can use git commit -s and the Git will handle it automatically).

We need signed-off commits for sending changes to the upstream.

To @xvitaly, I've squashed the fix into the main commit and signed-off as requested, please just check if anything else is missing.

Big thanks for your PR! Looks great for me One negligible comment: may you update the README for users how to install both libraries with CMake components (like "sudo cmake --install qrcodegen-build --component qrcodegencpp")

To @leha-bot, I've added the instructions concerning the CMake components, let me know if it blends well into the rest.

Thanks to both,
Cheers!

[xvitaly]

LGTM now. Thanks for your contribution.

[delta512]

My pleasure!

Thank you all for reacting so quickly, I can keep pulling from upstream in my PKGBUILD. 😎

Hasta la vista!