Autotools update

Attempt to handle the case when HDF5 is available from the environment (CPPFLAGS, LIBS etc.) but no h5cc or h5pcc commands are available.

mentioned in issue #276 (closed)

That worked straight out of the box on the Cray system ! Well done. Are you happy with this solution on more sensible systems (i.e. cosma) as well ?

mentioned in commit 3e0294f6

Status changed to merged

Yes, I am happy with this as a general solution. It works as before on COSMA.