add include dir for mpich

I guess it can't hurt to have too many include dirs, unless someone has
all of them... I'm not gonna worry about that now.

setup.py

@@ -30,6 +30,7 @@ local_install_dir = '/scratch.local/chichi/installs'
 
 include_dirs = ['src',
                 '/usr/lib64/mpi/gcc/openmpi/include',
+                '/usr/include/mpich',
                 os.path.join(local_install_dir, 'include')]
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