build sytem: add `--no-warn-rwx-segments` to linker

[maribu]

Contribution description

Before we disabled the warning about RWX segments only for picolibc, but this issue is popping up on more and more toolchains (looking at MSP430 and RISC-V). Other than on native/native64, there is no MMU to enforce whatever permissions the segments contain anyway. (And writing to ROM with regular store instructions will not be possible even without the need for an MMU.)

So let's just globally disable this warning, unless building for native and native64.

Testing procedure

Building in master with https://github.com/RIOT-OS/riotdocker/pull/248 will issue the RWX warning for every app now. And so does building on Alpine for MSP430.

With this PR the in our context not helpful warning is disabled.

Issues/PRs references

Not necessary, but useful for https://github.com/RIOT-OS/riotdocker/pull/248

[riot-ci]

Murdock results

:heavy_check_mark: PASSED

c9f16f1194573efa9c57b1722602a2174571d764 build sytem: add --no-warn-rwx-segments to linker

Success	Failures	Total	Runtime
10011	0	10011	11m:33s

Artifacts

• Documentation preview

[maribu]

Thx :)