Merge bitcoin/bitcoin#31121: guix: Enable CET for glibc package

4d3da08 guix: Enable CET for `glibc` package (Hennadii Stepanov)

Pull request description:

  Pulled from #30685. This doesn't need to wait for anything.

ACKs for top commit:
  laanwj:
    ACK 4d3da08
  TheCharlatan:
    ACK 4d3da08

Tree-SHA512: 1f4645971381fd342adec52c826fc0023722519a3e28043c9fe8b64bbc1abad822fcc25a64f3f959e3f3a10f5c119029f4cae13c22bac6badcbec9ae8b501dfc

Author: fanquake

contrib/guix/manifest.scm

@@ -469,6 +469,7 @@ inspecting signatures in Mach-O binaries.")
           `(append ,flags
             ;; https://www.gnu.org/software/libc/manual/html_node/Configuring-and-compiling.html
             (list "--enable-stack-protector=all",
+                  "--enable-cet",
                   "--enable-bind-now",
                   "--disable-werror",
                   building-on)))