jansson: enable shared library installation

[trofi]

Without shared libraries metworkmanager fails to build:

$ nix build -f. networkmanager -L
...
networkmanager> meson.build:269:2: ERROR: Assert failed: Unable to determine Jansson SONAME

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.11 Release Notes (or backporting 22.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[marsam]

LGTM. Thank you!

[github-actions]

Backport failed for release-22.05, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin release-22.05
git worktree add -d .worktree/backport-177063-to-release-22.05 origin/release-22.05
cd .worktree/backport-177063-to-release-22.05
git checkout -b backport-177063-to-release-22.05
ancref=$(git merge-base d07b20daf3b496bfd9121c67eefb504e26ca7ac6 938f2ce1017ff1fdb25abec3f22a0821618af8cb)
git cherry-pick -x $ancref..938f2ce1017ff1fdb25abec3f22a0821618af8cb

[vcunat]

Well the backport is trivial, but I'm waiting for confirmation that the version update really should be backported.

[github-actions]

Successfully created backport PR #177956 for staging-22.05.

[marsam]

I backported it because it's mostly an expression rewrite, which would help automatizing backports with labels.
I've checked the changes and it didn't contain any breaking change, except for this missing cmakeflag.

[vcunat]

I wasn't sure at a quick glance, with the way version number changed, and I'm not familiar with implications of symbol versioning in libs.