GCC Configuration

[spophale]

I don't know whether you also want to do this separation also for GCC; by default, GCC compiles for all configured offloading devices - which is usually "none" or a specific one, but the compilers by SUSE and Debian/Ubuntu provide (if the necessary optional packages are installed) support for both AMD GCN and nvptx. – The binaries are multi-arch binaries, which support all compiled-in offloading targets (+ host fallback).

GCC

nvptx: -foffload=nvptx-none can be used to force nvptx offloading (and disabling other offloading targets); GCC (since GCC 11?) often requires -foffload=-latomic (or -foffload=nvptx-none=-latomic) to link libatomic.
AMD GCN: -foffload=amdgcn-amdhsa + -foffload=-march=fiji or likewise for gfx900, gfx906, or gfx908 (or -foffload=amdgcn-amdhsa=-march=... - if you compile for multiple offload targets at the same time.)