[RFC] zstd as a compression algorithm for LTO

[Thomas Koenig]

Hi Martin,

> LTO bytecode is not supposed to be a distributable format.

One of my dreams is to make libgfortran LTO-clean.  There is
a lot of performance to be gained both in I/O (where a huge
number of special cases could be shortcut by LTO, because
hardly any program uses them all) and in array intrinsics,
where seeing through the array descriptors can also lead
to large benefits.  This is PR 77278.

Once this is achieved, it would make sense to distribute
libgfortran.a as a library of fat object files.

Regards

	Thomas