Build only shared library for CFEP-18 compliance

[traversaro]

Furthermore, as explained in https://github.com/conda-forge/libosqp-feedstock/issues/4#issuecomment-853151791 this change actually ensure that downstream consumers of the library on Windows use the shared library instead of linking the static one.

Fix https://github.com/conda-forge/libosqp-feedstock/issues/4 . The patch to realize this was proposed upstream in https://github.com/oxfordcontrol/osqp/pull/310 .

Note that in this case we don't have the problem described in https://github.com/osqp/osqp/issues/309#issuecomment-853157002 as we are using NMake Makefiles as CMake generator.

Checklist

• [x] Used a personal fork of the feedstock to propose changes
• [x] Bumped the build number (if the version is unchanged)
• [ ] Reset the build number to 0 (if the version changed)
• [x] Re-rendered with the latest conda-smithy (Use the phrase code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [x] Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[traversaro]

@conda-forge-admin, please rerender

[traversaro]

fyi @Levi-Armstrong @johnwason