Set # of ninja procs to 'make_jobs' for scipy (#293) (#38831)

var/spack/repos/builtin/packages/py-scipy/package.py

@@ -241,6 +241,7 @@ def install(self, spec, prefix):
             "-Cbuilddir=build",
             "--no-isolation",
             "--skip-dependency-check",
+            "-Ccompile-args=-j%s" % make_jobs,
             ".",
         ]
         python(*args)