MKL fix for mac

[ajaypanyala]

macOS linker does not support --{start,end}-group
The IntelMKL link line advisor also does not suggest these options when macOS is selected.

[ajaypanyala]

@wavefunction91 This PR is tested on an Intel MAC. MKL is obviously not supported on the new M1,M2 (Arm) macs. Should we just throw an error if a MAC is detected preventing MKL discovery completely or allow discovery for intel based macs (maybe by checking the processor) ?

[wavefunction91]

By MacOS linker, do you mean AppleClang? Or is this some strange Mac specific thing that infects all compilers? We can definitely do a processor or OS check if it's the latter, compiler check if the former.

[ajaypanyala]

Since GNU ld is not supported on macOS, the default linker on macOS is used regardless of the compiler (am using brew installed gcc-12 in this case for testing). Added a check to detect arm64 and report error.

[wavefunction91]

Adding a FATAL_ERROR on arm64 would bring down the whole application - I'd just have it "try" to search for MKL, fail, and move on with its day. We could add an early exit condition if we're really concerned about MKL existing on ARM environments, but a failed check isn't a large overhead

[ajaypanyala]

Changed it to a warning.