guix: build GCC with --enable-standard-branch-protection
Summary:
To enable Branch Target Identification Mechanism and Return Address Signing by default at configure time use the `--enable-standard-branch-protection` option. This is equivalent to having `-mbranch-protection=standard` during compilation. This can be explicitly disabled during compilation by passing the `-mbranch-protection=none` option which turns off all types of branch protections. See: https://gcc.gnu.org/install/specific.html#aarch64-x-x
Backport of core#29695.
Depends on D17231.
Test Plan: Run the linux guix build.
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D17232