Fix CodeQL cpp build failure by linking libyang

[Copilot]

Description of PR

Summary:
Resolve the failing CodeQL / Analyze (cpp) job caused by a link-time dependency gap after swsscommon moved to libyang.so.3.
This PR adds libyang to the link set used for linkmgrd binaries.

Type of change

• Bug fix
• New feature
• Doc/Design
• Unit test

Approach

What is the motivation for this PR?

The CodeQL C++ workflow fails during the build phase (before analysis) with undefined ly_* symbols from libswsscommon.so, indicating libyang is required but not linked by this repo.

Work item tracking

• Microsoft ADO (number only): N/A

How did you do it?

• Root-cause fix
  • Updated linker libraries in objects.mk to include -lyang in LIBS.
• Scope
  • Single-file, minimal build-system change; no source logic changes.

LIBS := \
    -lswsscommon \
    -lyang \
    -lboost_date_time \

How did you verify/test it?

Confirmed the generated release-targets linker command now contains -lyang, which addresses the missing libyang.so.3 symbols seen in the failing job logs.

Any platform specific information?

Targets the Ubuntu GitHub Actions environment used by CodeQL where swsscommon links against libyang.so.3.

Documentation

No documentation update required (build/link dependency correction only).

[mssonicbld]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).