cons: Use mysql_config to set up external dependency for mysql

[plexoos]

When we configure the build with mysql as external dependency we can fully rely on mysql_config found in PATH

This is similar to #357 where we also use config utilities to set up fastjet and gsl packages.

[klendathu2k]

Seems reasonable. Only issue is that if we need to build against a specific mysql install... it needs to be located in the path before /usr/bin/mysql_config. (Presumably managed by spack or ...)

[plexoos]

In case someone wants to use a specific mysql install, the same principle would apply, i.e. they just update/prepend their PATH with the location of their mysql_config. It is not very different from setting an additional variable such as USE_LOCAL_MYSQL

P.S. It is a bit hard to imagine a volunteer who would like to experiment with a new version of mysql client. I think at this moment in STAR history the focus is more on the environment preservation rather than a new R&D... But the possibility is not closed with this update.

[plexoos]

Gene, do you have any objections to the changes?

[genevb]

Gene, do you have any objections to the changes?

I don't know enough about this to object to the implementation. I don't have any objections to the idea of enabling flexible handling of mysql dependency as long as people compiling root4star outside of SDCC/RCF don't end up having complications and confusion.

[genevb]

No bjections

[plexoos]

Thank you for your feedback. I asked because you are a designated maintainer of this code in mgr/ Of course it can be changed at any time at your will.
If there are any specific concerns with installation of star-sw on a supported system we'll deal with them when details become available.

I'll interpret this response as an approval for these specific changes and in the similar PRs: #402, #404, and #405