Bug#1102472: python3-torch: -march=native leaks into rdeps

[Adrian Bunk <bunk@debian.org>]

Package: python3-torch
Version: 2.6.0+dfsg-5
Severity: serious
Control: affects src:pytorch-geometric

The pytorch-geometric autopkgtest fails, preventing migration to trixie:

https://ci.debian.net/packages/p/pytorch-geometric/testing/riscv64/

...
2171s E           
2171s E           Output:
2171s E           g++: error: ‘-march=native’: ISA string must begin with rv32 or rv64
...


Leaking -march=native into rdeps, since it mustn't be used in
package builds.

(Using it in tests is OKish, but it's not supported on all architectures.)

The root cause of the pytorch-geometric problem is
_get_optimization_cflags() in 
/usr/lib/python3/dist-packages/torch/_inductor/cpp_builder.py