Detect number of processors for make

# make the library via Makefile.auto

try:

  import multiprocessing

  n_cpus = multiprocessing.cpu_count()

except:

  n_cpus = 1

print("Building lib%s.a ..." % lib)

cmd = ["make -f Makefile.auto clean"]

print(subprocess.check_output(cmd, shell=True).decode())

cmd = ["make -f Makefile.auto -j12"]

cmd = ["make -f Makefile.auto -j%d" % n_cpus]

print(subprocess.check_output(cmd, shell=True).decode())

if os.path.exists("lib%s.a" % lib): print("Build was successful")