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

首先使用 ./configure --enable-experimental-jit=yes-off CFLAGS="-fcf-protection" && make -j 重现该问题，然后使用 readelf -n 检查 JIT shim 对象和生成的 python 二进制文件。跟踪 commit 9633c5239daa 之后 jit_shim.o 如何作为普通对象构建。对于报告的 x86 和 aarch64 安全特性，GNU property notes 仍保留在输出二进制文件中，即表示完成。