JIT shim object drops GNU property notes (CET/BTI/PAC) from output binaries

Bug report

Bug description:

When building with --enable-experimental-jit the jit_shim.o object lacks GNU property notes for hardware security features. The linker removes all such properties from the output binaries when any input object lacks them.

The regression was introduced with 9633c5239daa which makes the shim being compiled as a regular object file.

You can reproduce it by using ./configure --enable-experimental-jit=yes-off CFLAGS="-fcf-protection" && make -j.

Before the aforementioned commit a readelf -n python | grep 'x86 feature' would show Properties: x86 feature: IBT, SHSTK, whereas now nothing.

This is the case as well for BTI/PAC/GCS for aarch64 when building with https://github.com/python/cpython/pull/130864 and -mbranch-protection=standard.

My testing included GCC15.2.1 for the interpreter and Clang 21.1.8 for the jit, on Fedora 43.

CPython versions tested on:

3.16, CPython main branch, 3.15

Operating systems tested on:

Linux

Inizia riproducendo il problema con ./configure --enable-experimental-jit=yes-off CFLAGS="-fcf-protection" && make -j, quindi esamina l'oggetto shim del JIT e il binario python risultante con readelf -n. Traccia il modo in cui jit_shim.o viene compilato come oggetto regolare dopo il commit 9633c5239daa. Il lavoro è completato quando le GNU property notes rimangono nei binari di output per le funzionalità di sicurezza x86 e aarch64 segnalate.