[hotfix] OpenCL ThreadInfo option fixed for Automatic Reductions

[jjfumero]

Description

Thread info was disabled for single-thread OpenCL generated programs. This PR supports debug info also for single thread kernels. This is reachable from automatic reductions in the final merge step, for example.

This fixes issue #197

Backend/s tested

This PR only affects the OpenCL Backend

• [X] OpenCL
• [ ] PTX
• [ ] SPIRV

OS tested

Mark the OS where this PR is tested.

• [X] Linux
• [ ] OSx
• [ ] Windows

Did you check on FPGAs?

If it is applicable, check your changes on FPGAs.

• [ ] Yes
• [X] No

How to test the new patch?

$ make BACKEND=opencl
$ tornado --threadInfo -ea -Dtornado.unittests.verbose=True -Xmx6g -Dtornado.recover.bailout=False  -m  tornado.unittests/uk.ac.manchester.tornado.unittests.tools.TornadoTestRunner  uk.ac.manchester.tornado.unittests.reductions.TestReductionsFloats#testComputeAverage

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[jjfumero]

Note: first we need to merge #196