gcc compilers to be supported by Macports, especially on older MacOS systems

[Chris Jones]

> So the very first thing that someone should do is fix these three ports
> 
> libgcc8
> libgcc10
> libgcc11

See

https://github.com/macports/macports-ports/commit/eea28397c811c477a04407cbe3c105c76efd9219

https://github.com/macports/macports-ports/commit/06e249f837f36a877ea5dc0dd67d7b0caf964c40

( Note I was wrong about libgcc8, it is already properly configured as a 
stub port )

With that, considering gcc version 7 through to 14, the only real 
builds, so removing all the stubs are

gccN
libgcc14
libgcc9
libgcc7

So for any GCC version a user might request between 10 and 14, they will 
only need to build two ports, one runtime (libgcc14, shared for all of 
them) and the specific gcc version requested. Given how we split the 
compiler from the runtime, this is as good as it can get.

For gcc9, you will need to build gcc9, libgcc9 and libgcc14

For gcc7, you will need to build gcc7, libgcc7, libgcc9 and libgcc14

So, as far as I see it the best way you can minimize the number of gcc 
versions you need to build on these ancient systems, is to migrate as 
many builds as you can to use gcc10 or gcc14 (the two newest ones in the 
list you sent around), as then you are already in the best case scenario 
(two builds). I see no compelling reason to change the dependency tree 
in the libgccN versions.

Chris