Disable fvisibility=hidden with PGI

[DavidPoliakoff]

PGI doesn't support this flag

[mplegendre]

Should we support building with PGI at all?

Gotcha doesn't have the ABI compatibility problems, performance restrictions, or accelerator support requirements that other software does. I'd be tempted to just tell people to build with gcc.

[DavidPoliakoff]

The problem is in how other applications build us. For example, if Caliper is a part of HydroCode, and HydroCode is building with PGI, then they'll build Caliper with PGI, which will then pull down Gotcha and forward the compiler choice to us. We could tell users to not build us with the compiler they're built with, but it's pretty non-idiomatic. I think we could get friendly users like @daboehme to do so, but if it's not too much effort, I'd like to support a broad range of compilers.

[mplegendre]

There are plenty of libraries that don't build with PGI. I don't think there would be major issues making another.