[skip-ci] set OMP_NUM_THREADS=1 globally

tools/__init__.py

 import os
 os.environ['OPENBLAS_NUM_THREADS'] = '1'
+os.environ['OMP_NUM_THREADS'] = '1'
+
 # os.environ['RWROOT']=os.path.join(os.path.dirname(__file__), "../../../../../")
 
 __path__ = __import__('pkgutil').extend_path(__path__, __name__)