[Bug target/104857] [nvptx] Add macro specifying ptx isa version

[vries at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104857

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Created attachment 52592
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52592&action=edit
Tentative patch