Hi Shrenik,
I checked OpenBLAS's Makefile.system and found that USE_THREAD is overridden to 0 if it is built on a single core machine. I just added a patch so that USE_OPENMP should be also overridden to 0 in such case.
https://lab.nexedi.com/nexedi/slapos/commit/73f9574f4a9868d468693432575330231f750353