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

Beginne damit, das Problem mit ./configure --enable-experimental-jit=yes-off CFLAGS="-fcf-protection" && make -j zu reproduzieren, und untersuche dann das JIT-Shim-Objekt und die resultierende python-Binärdatei mit readelf -n. Verfolge, wie jit_shim.o nach Commit 9633c5239daa als reguläres Objekt gebaut wird. Als erledigt gilt die Aufgabe, wenn GNU property notes in den Ausgabebinärdateien für die gemeldeten x86- und aarch64-Sicherheitsfunktionen erhalten bleiben.