Fix MKL build issue by correctly finding and linking MKL libraries

[green-dalii]

Fix MKL Build Issue

Description

This pull request fixes an issue with building whisper.cpp using Intel MKL. The changes ensure that CMake correctly finds and links the MKL libraries.

Changes Made

• Added find_package(MKL REQUIRED) to locate MKL.
• Set MKL_INCLUDE_DIRS and MKL_LIBRARIES to ensure proper include and link paths.
• Included MKL headers and libraries only if WHISPER_MKL is enabled.

Testing

Successfully built whisper.cpp with the MKL option enabled on an Intel Xeon CPU without GPU.

Related Issues

Fixes # (if applicable)