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