Merge #18629: scripts: add PE .reloc section check to security-check.py

3e38023af724a76972d39cbccfb0bba4c54a0323 scripts: add PE .reloc section check to security-check.py (fanquake)

Pull request description:

  The `ld` in binutils has historically had a few issues with PE binaries, there's a good summary in this [thread](https://sourceware.org/bugzilla/show_bug.cgi?id=19011).

  One issue in particular was `ld` stripping the `.reloc` section out of PE binaries, even though it's required for functioning ASLR. This was [reported by a Tor developer in 2014](https://sourceware.org/bugzilla/show_bug.cgi?id=17321) and they have been patching their [own binutils](https://gitweb.torproject.org/builders/tor-browser-build.git/tree/projects/binutils) ever since. However their patch only made it into binutils at the [start of this year](https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=dc9bd8c92af67947db44b3cb428c050259b15cd0). It adds an `--enable-reloc-section` flag, which is turned on by default if you are using `--dynamic-base`. In the mean time this issue has also been worked around by other projects, such as FFmpeg, see [this commit](https://github.com/TheRyuu/FFmpeg/commit/91b668acd6decec0a6f8d20bf56e2644f96adcb9).

  I have checked our recent supported Windows release binaries, and they do contain a `.reloc` section. From what I understand, we are using all the right compile/linker flags, including `-pie` & `-fPIE`, and have never run into the crashing/entrypoint issues that other projects might have seen.

  One other thing worth noting here, it how Debian/Ubuntu patch the binutils that they distribute, because that's what we end up using in our gitian builds.

  In the binutils-mingw-w64 in Bionic (18.04), which we currently use in gitian, PE hardening options/security flags are enabled by default. See the [changelog](https://changelogs.ubuntu.com/changelogs/pool/universe/b/binutils-mingw-w64/binutils-mingw-w64_8ubuntu1/changelog) and the [relevant commit](https://salsa.debian.org/mingw-w64-team/binutils-mingw-w64/-/commit/452b3013b8280cbe35eaeb166a43621b88d5f8b7).

  However in Focal (20.04), this has now been reversed. PE hardening options are no-longer the default. See the [changelog](https://changelogs.ubuntu.com/changelogs/pool/universe/b/binutils-mingw-w64/binutils-mingw-w64_8.8/changelog) and [relevant commit](https://salsa.debian.org/mingw-w64-team/binutils-mingw-w64/-/commit/7bd8b2fbc242a8c2fc2217f29fd61f94d3babf6f), which cites same .reloc issue mentioned here.

  Given that we explicitly specify/opt-in to everything that we want to use, the defaults aren't necessarily an issue for us. However I think it highlights the importance of continuing to be explicit about what we want, and not falling-back or relying on upstream.

  This was also prompted by the possibility of us doing link time garbage collection, see #18579 & #18605. It seemed some sanity checks would be worthwhile in-case the linker goes haywire while garbage collecting.

  I think Guix is going to bring great benefits when dealing with these kinds of issues. Carl you might have something to say in that regard.

ACKs for top commit:
  dongcarl:
    ACK 3e38023af724a76972d39cbccfb0bba4c54a0323

Tree-SHA512: af14d63bdb334bde548dd7de3e0946556b7e2598d817b56eb4e75b3f56c705c26aa85dd9783134c4b6a7aeb7cb4de567eed996e94d533d31511f57ed332287da

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