Updates to netcdf-cxx4 tool

[isabels]

No description provided.

[garyjg]

It is unusual for a tool to create a variable only if pkg-config fails. It means the developer cannot use the variable at all if pkg-config happens to succeed, which at the least might make testing difficult and also is probably not what someone expects. If the variable is definitely not useful on OSX, then I guess it might make sense to not to create there, but if there's a chance it could be useful, then I suggest always creating the NETCDFCXX4DIR variable, with a default of None. The None default implies use the platform-specific default: no change on Darwin, pkg-config if it works, and otherwise /opt/local. Then a developer can set it explicitly anywhere, and if set it will be used as is, regardless of platform or pkg-config state. Otherwise the default works everywhere, and there's no confusion about when the variable should or shouldn't exist. Thoughts?

[isabels]

Now that it looks like there's a package for netcdf-cxx4 on alma9, there's no current need for the NETCDFCXX4DIR variable. Should I get rid of it, or should we keep in case it's useful later?

[garyjg]

I think the variable can still be useful, in particular I've been using it to test against the latest netcdf-cxx4 built from source. So I've left it in and expanded the search to find "lib64/libnetcdf-cxx4.so" on Fedora. Hopefully, this works the same as before when NETCDFCXX4DIR is not set, including on MacOS and Windows.