Further improvements in dependency stack management. The script works in a Linux environment that lacks the two

default, primary OpenCoarrays build prerequisites CMake and MPICH and all additional software in the resulting
chain of prerequisites, including 'flex' which is present but with a version number lower than the version
required and which therefore must be built from source.  The MPICH build fails because executables built by
gfortran cannot access the find the shared library libgfortran.so.3.  The latter error must be researched and
resolved.

Signed-off-by: Damian Rouson <[email protected]>

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Author: Damian Rouson